Adding upstream version 1:2.3.21+dfsg1.upstream/1%2.3.21+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

30 files changed, 12340 insertions, 0 deletions

diff --git a/src/lib-storage/list/Makefile.am b/src/lib-storage/list/Makefile.am
new file mode 100644
index 0000000..3a15e8e
--- /dev/null
+++ b/src/lib-storage/list/Makefile.am
@@ -0,0 +1,45 @@
+noinst_LTLIBRARIES = libstorage_list.la
+
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+	-I$(top_srcdir)/src/lib \
+	-I$(top_srcdir)/src/lib-fs \
+	-I$(top_srcdir)/src/lib-mail \
+	-I$(top_srcdir)/src/lib-index \
+	-I$(top_srcdir)/src/lib-imap \
+	-I$(top_srcdir)/src/lib-storage \
+	-I$(top_srcdir)/src/lib-storage/index
+
+libstorage_list_la_SOURCES = \
+	mail-storage-list-index-rebuild.c \
+	mailbox-list-delete.c \
+	mailbox-list-fs.c \
+	mailbox-list-fs-flags.c \
+	mailbox-list-fs-iter.c \
+	mailbox-list-index.c \
+	mailbox-list-index-backend.c \
+	mailbox-list-index-iter.c \
+	mailbox-list-index-notify.c \
+	mailbox-list-index-status.c \
+	mailbox-list-index-sync.c \
+	mailbox-list-iter.c \
+	mailbox-list-maildir.c \
+	mailbox-list-maildir-iter.c \
+	mailbox-list-none.c \
+	mailbox-list-notify-tree.c \
+	mailbox-list-subscriptions.c \
+	subscription-file.c
+
+headers = \
+	mailbox-list-delete.h \
+	mailbox-list-fs.h \
+	mailbox-list-index.h \
+	mailbox-list-index-storage.h \
+	mailbox-list-index-sync.h \
+	mailbox-list-iter-private.h \
+	mailbox-list-maildir.h \
+	mailbox-list-notify-tree.h \
+	mailbox-list-subscriptions.h \
+	subscription-file.h
+
+pkginc_libdir=$(pkgincludedir)
+pkginc_lib_HEADERS = $(headers)
diff --git a/src/lib-storage/list/Makefile.in b/src/lib-storage/list/Makefile.in
new file mode 100644
index 0000000..37ec2ca
--- /dev/null
+++ b/src/lib-storage/list/Makefile.in
@@ -0,0 +1,916 @@
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+	-rm -f ./$(DEPDIR)/subscription-file.Plo
+	-rm -f Makefile
+maintainer-clean-am: distclean-am maintainer-clean-generic
+
+mostlyclean: mostlyclean-am
+
+mostlyclean-am: mostlyclean-compile mostlyclean-generic \
+	mostlyclean-libtool
+
+pdf: pdf-am
+
+pdf-am:
+
+ps: ps-am
+
+ps-am:
+
+uninstall-am: uninstall-pkginc_libHEADERS
+
+.MAKE: install-am install-strip
+
+.PHONY: CTAGS GTAGS TAGS all all-am am--depfiles check check-am clean \
+	clean-generic clean-libtool clean-noinstLTLIBRARIES \
+	cscopelist-am ctags ctags-am distclean distclean-compile \
+	distclean-generic distclean-libtool distclean-tags distdir dvi \
+	dvi-am html html-am info info-am install install-am \
+	install-data install-data-am install-dvi install-dvi-am \
+	install-exec install-exec-am install-html install-html-am \
+	install-info install-info-am install-man install-pdf \
+	install-pdf-am install-pkginc_libHEADERS install-ps \
+	install-ps-am install-strip installcheck installcheck-am \
+	installdirs maintainer-clean maintainer-clean-generic \
+	mostlyclean mostlyclean-compile mostlyclean-generic \
+	mostlyclean-libtool pdf pdf-am ps ps-am tags tags-am uninstall \
+	uninstall-am uninstall-pkginc_libHEADERS
+
+.PRECIOUS: Makefile
+
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/src/lib-storage/list/mail-storage-list-index-rebuild.c b/src/lib-storage/list/mail-storage-list-index-rebuild.c
new file mode 100644
index 0000000..c55cf82
--- /dev/null
+++ b/src/lib-storage/list/mail-storage-list-index-rebuild.c
@@ -0,0 +1,615 @@
+/* Copyright (c) 2021 Dovecot Authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hash.h"
+#include "guid.h"
+#include "mail-namespace.h"
+#include "str.h"
+#include "str-sanitize.h"
+#include "hex-binary.h"
+#include "randgen.h"
+#include "fs-api.h"
+#include "mail-index.h"
+#include "mailbox-list-index.h"
+#include "mailbox-list-index-sync.h"
+#include "mailbox-tree.h"
+#include "mail-storage-private.h"
+#include "strfuncs.h"
+
+struct mail_storage_list_index_rebuild_mailbox {
+	guid_128_t guid;
+	const char *index_name;
+	const char *storage_name;
+	struct mailbox_list *list;
+};
+
+struct mail_storage_list_index_rebuild_ns {
+	struct mail_namespace *ns;
+	struct mailbox_list_index_sync_context *list_sync_ctx;
+};
+
+struct mail_storage_list_index_rebuild_ctx {
+	struct mail_storage *storage;
+	pool_t pool;
+	HASH_TABLE(char*, struct mail_storage_list_index_rebuild_mailbox *) mailboxes;
+	ARRAY(struct mail_storage_list_index_rebuild_ns) rebuild_namespaces;
+};
+
+static bool
+mail_storage_list_index_rebuild_get_namespaces(struct mail_storage_list_index_rebuild_ctx *ctx)
+{
+	struct mail_namespace *ns;
+	struct mail_storage_list_index_rebuild_ns *rebuild_ns;
+
+	p_array_init(&ctx->rebuild_namespaces, ctx->pool, 4);
+	for (ns = ctx->storage->user->namespaces; ns != NULL; ns = ns->next) {
+		if (ns->storage != ctx->storage ||
+		    ns->alias_for != NULL)
+			continue;
+
+		/* ignore any non-INDEX layout */
+		if (strcmp(ns->list->name, MAILBOX_LIST_NAME_INDEX) != 0)
+			continue;
+
+		rebuild_ns = array_append_space(&ctx->rebuild_namespaces);
+		rebuild_ns->ns = ns;
+	}
+
+	return array_count(&ctx->rebuild_namespaces) > 0;
+}
+
+static int rebuild_ns_cmp(const struct mail_storage_list_index_rebuild_ns *ns1,
+			  const struct mail_storage_list_index_rebuild_ns *ns2)
+{
+	return strcmp(ns1->ns->prefix, ns2->ns->prefix);
+}
+
+static int
+mail_storage_list_index_rebuild_lock_lists(struct mail_storage_list_index_rebuild_ctx *ctx)
+{
+	struct mail_storage_list_index_rebuild_ns *rebuild_ns;
+
+	/* sort to make sure all processes lock the lists in the same order
+	   to avoid deadlocks. this should be the only place that locks more
+	   than one list. */
+	array_sort(&ctx->rebuild_namespaces, rebuild_ns_cmp);
+
+	array_foreach_modifiable(&ctx->rebuild_namespaces, rebuild_ns) {
+		if (mailbox_list_index_sync_begin(rebuild_ns->ns->list,
+						  &rebuild_ns->list_sync_ctx) < 0) {
+			mail_storage_copy_list_error(ctx->storage,
+						     rebuild_ns->ns->list);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static void
+mail_storage_list_index_rebuild_unlock_lists(struct mail_storage_list_index_rebuild_ctx *ctx)
+{
+	struct mail_storage_list_index_rebuild_ns *rebuild_ns;
+
+	array_foreach_modifiable(&ctx->rebuild_namespaces, rebuild_ns) {
+		if (rebuild_ns->list_sync_ctx != NULL)
+			(void)mailbox_list_index_sync_end(&rebuild_ns->list_sync_ctx, TRUE);
+	}
+}
+
+static bool try_get_mailbox_name(struct mail_storage_list_index_rebuild_ctx *ctx,
+				 struct mailbox_list *list, const char *path,
+				 const char **name_r)
+{
+	struct mail_index *index =
+		mail_index_alloc(ctx->storage->event, path, MAIL_INDEX_PREFIX);
+	struct mail_index_view *view;
+	uint32_t box_name_hdr_ext_id;
+	bool ret = FALSE;
+	int rc;
+	if ((rc = mail_index_open(index, MAIL_INDEX_OPEN_FLAG_READONLY)) > 0) {
+		if (mail_index_ext_lookup(index, "box-name", &box_name_hdr_ext_id)) {
+			view = mail_index_view_open(index);
+			const void *name_hdr;
+			size_t name_hdr_size;
+			mail_index_get_header_ext(view, box_name_hdr_ext_id,
+						  &name_hdr, &name_hdr_size);
+			*name_r = mailbox_name_hdr_decode_storage_name(list,
+							name_hdr, name_hdr_size);
+			ret = TRUE;
+			mail_index_view_close(&view);
+		} else {
+			e_debug(ctx->storage->event,
+				"Cannot find box-name extension in mailbox index at %s", path);
+		}
+		mail_index_close(index);
+	} else if (rc == 0) {
+		e_debug(ctx->storage->event, "Cannot open mailbox index at %s: Not found", path);
+	} else if (rc < 0) {
+		e_debug(ctx->storage->event, "Cannot open mailbox index at %s: %s",
+			path, mail_index_get_error_message(index));
+	}
+	mail_index_free(&index);
+	return ret;
+}
+
+static const char *get_box_name(struct mail_storage_list_index_rebuild_ctx *ctx,
+				struct mail_storage_list_index_rebuild_mailbox *box)
+{
+	const char *path =
+		t_strdup_printf("%s/%s",
+				mailbox_list_get_root_forced(box->list, MAILBOX_LIST_PATH_TYPE_MAILBOX),
+				guid_128_to_string(box->guid));
+	const char *box_name;
+	bool inbox_ns = (box->list->ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0;
+
+	if (try_get_mailbox_name(ctx, box->list, path, &box_name)) {
+		/* special case handling */
+		if (inbox_ns && strcmp(box_name, "INBOX") == 0)
+			box_name = "INBOX";
+		e_debug(ctx->storage->event, "Found '%s' from storage %s",
+			box_name, path);
+	} else {
+		e_debug(ctx->storage->event, "Found GUID '%s' from storage %s, "
+					     "but could not recover mailbox name",
+			guid_128_to_string(box->guid), path);
+		box_name = t_strdup_printf("%s%s",
+					   ctx->storage->lost_mailbox_prefix,
+					   guid_128_to_string(box->guid));
+	}
+	return box_name;
+}
+
+static int
+mail_storage_list_index_fill_storage_mailboxes(struct mail_storage_list_index_rebuild_ctx *ctx,
+					       struct mailbox_list *list)
+{
+	struct mail_storage_list_index_rebuild_mailbox *box;
+	struct fs_iter *iter;
+	const char *path, *fname, *error;
+	guid_128_t guid;
+
+	path = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_MAILBOX);
+	iter = fs_iter_init_with_event(ctx->storage->mailboxes_fs,
+				       ctx->storage->event, path,
+				       FS_ITER_FLAG_DIRS | FS_ITER_FLAG_NOCACHE);
+	while ((fname = fs_iter_next(iter)) != NULL) T_BEGIN {
+		if (guid_128_from_string(fname, guid) == 0) {
+			box = p_new(ctx->pool, struct mail_storage_list_index_rebuild_mailbox, 1);
+			guid_128_copy(box->guid, guid);
+			e_debug(ctx->storage->event,
+				"Found GUID '%s' from storage %s",
+				guid_128_to_string(guid), path);
+			char *hk = p_strdup_printf(ctx->pool, "%s%s",
+						   list->ns->prefix,
+						   guid_128_to_string(guid));
+			box->list = list;
+			hash_table_update(ctx->mailboxes, hk, box);
+		}
+	} T_END;
+
+	if (fs_iter_deinit(&iter, &error) < 0) {
+		mail_storage_set_critical(ctx->storage,
+			"List rebuild: fs_iter_deinit(%s) failed: %s", path,
+			error);
+		return -1;
+	}
+	return 0;
+}
+
+static int
+mail_storage_list_remove_duplicate(struct mail_storage_list_index_rebuild_ctx *ctx,
+				   struct mail_storage_list_index_rebuild_ns *rebuild_ns,
+				   struct mailbox *box,
+				   struct mail_storage_list_index_rebuild_mailbox *rebuild_box)
+{
+	const char *delete_name, *keep_name;
+
+	if (strcmp(box->list->name, MAILBOX_LIST_NAME_INDEX) != 0) {
+		/* we're not using LAYOUT=index. not really supported now,
+		   but just ignore that in here. */
+		return 0;
+	}
+	/* we'll need to delete one of these entries. if one of them begins with
+	   "lost-", remove it. otherwise just pick one of them randomly. */
+	if (strncmp(box->name, ctx->storage->lost_mailbox_prefix,
+		    strlen(ctx->storage->lost_mailbox_prefix)) == 0) {
+		delete_name = box->name;
+		keep_name = rebuild_box->index_name;
+	} else {
+		delete_name = rebuild_box->index_name;
+		keep_name = p_strdup(ctx->pool, box->name);
+	}
+
+	e_debug(ctx->storage->event,
+		"Removing duplicate mailbox '%s' in favor of mailbox '%s'",
+		str_sanitize(delete_name, 128), str_sanitize(keep_name, 128));
+
+	if (mailbox_list_index_sync_delete(rebuild_ns->list_sync_ctx,
+					   delete_name, TRUE) < 0) {
+		mail_storage_set_critical(ctx->storage,
+			"List rebuild: Couldn't delete duplicate mailbox list index entry %s: %s",
+			delete_name, mailbox_list_get_last_internal_error(box->list, NULL));
+		return -1;
+	}
+	e_warning(box->event, "List rebuild: Duplicated mailbox GUID %s found - deleting mailbox entry %s (and keeping %s)",
+		  guid_128_to_string(rebuild_box->guid), delete_name, keep_name);
+	rebuild_box->index_name = keep_name;
+	return 0;
+}
+
+static int
+mail_storage_list_index_find_indexed_mailbox(struct mail_storage_list_index_rebuild_ctx *ctx,
+					     struct mail_storage_list_index_rebuild_ns *rebuild_ns,
+					     const struct mailbox_info *info)
+{
+	struct mail_storage_list_index_rebuild_mailbox *rebuild_box;
+	struct mailbox *box;
+	struct mailbox_metadata metadata;
+	int ret = 0;
+
+	if ((info->flags & (MAILBOX_NOSELECT | MAILBOX_NONEXISTENT)) != 0)
+		return 0;
+
+	box = mailbox_alloc(info->ns->list, info->vname, MAILBOX_FLAG_IGNORE_ACLS);
+	if (mailbox_get_metadata(box, MAILBOX_METADATA_GUID, &metadata) < 0) {
+		mail_storage_set_critical(rebuild_ns->ns->storage,
+			"List rebuild: Couldn't lookup mailbox %s GUID: %s",
+			info->vname, mailbox_get_last_internal_error(box, NULL));
+		ret = -1;
+	} else {
+		const char *hk = t_strdup_printf("%s%s", info->ns->prefix,
+						 guid_128_to_string(metadata.guid));
+		rebuild_box = hash_table_lookup(ctx->mailboxes, hk);
+		if (rebuild_box == NULL) {
+			/* indexed but doesn't exist in storage. shouldn't
+			   happen normally, but it'll be created when it gets
+			   accessed. */
+			e_debug(box->event,
+				"Mailbox GUID %s exists in list index, but not in storage",
+				guid_128_to_string(metadata.guid));
+			/* Add it there so we can delete the duplicate */
+			char *hk_dup = p_strdup(ctx->pool, hk);
+			rebuild_box = p_new(ctx->pool, struct mail_storage_list_index_rebuild_mailbox, 1);
+			rebuild_box->list = info->ns->list;
+			rebuild_box->index_name = p_strdup(ctx->pool, box->name);
+			guid_128_copy(rebuild_box->guid, metadata.guid);
+			hash_table_insert(ctx->mailboxes, hk_dup, rebuild_box);
+		} else if (rebuild_box->index_name == NULL) {
+			rebuild_box->index_name =
+				p_strdup(ctx->pool, box->name);
+			e_debug(box->event,
+				"Mailbox GUID %s exists in list index and in storage",
+				guid_128_to_string(metadata.guid));
+		} else {
+			/* duplicate GUIDs in index. in theory this could be
+			   possible because of mailbox aliases, but we don't
+			   support that for now. especially dsync doesn't like
+			   duplicates. */
+			if (mail_storage_list_remove_duplicate(ctx, rebuild_ns,
+							       box, rebuild_box) < 0)
+				ret = -1;
+		}
+	}
+	mailbox_free(&box);
+	return ret;
+}
+
+static int
+mail_storage_list_index_find_indexed_mailboxes(struct mail_storage_list_index_rebuild_ctx *ctx,
+					       struct mail_storage_list_index_rebuild_ns *rebuild_ns)
+{
+	struct mailbox_list_iterate_context *iter;
+	const struct mailbox_info *info;
+	int ret = 0;
+
+	iter = mailbox_list_iter_init(rebuild_ns->ns->list, "*",
+				      MAILBOX_LIST_ITER_RAW_LIST |
+				      MAILBOX_LIST_ITER_NO_AUTO_BOXES |
+				      MAILBOX_LIST_ITER_SKIP_ALIASES);
+	while (ret == 0 && (info = mailbox_list_iter_next(iter)) != NULL) T_BEGIN {
+		ret = mail_storage_list_index_find_indexed_mailbox(ctx, rebuild_ns, info);
+	} T_END;
+	if (mailbox_list_iter_deinit(&iter) < 0) {
+		mail_storage_set_critical(rebuild_ns->ns->storage,
+			"List rebuild: Failed to iterate mailboxes: %s",
+			mailbox_list_get_last_internal_error(rebuild_ns->ns->list, NULL));
+		return -1;
+	}
+	return ret;
+}
+
+static int
+mail_storage_list_mailbox_create(struct mailbox *box,
+				 const struct mailbox_update *update)
+{
+	e_debug(box->event, "Attempting to create mailbox");
+	if (mailbox_create(box, update, FALSE) == 0)
+		return 1;
+
+	if (mailbox_get_last_mail_error(box) == MAIL_ERROR_NOTFOUND) {
+		/* if this is because mailbox was marked as deleted,
+		   undelete it and retry. */
+		if (mailbox_mark_index_deleted(box, FALSE) < 0)
+			return -1;
+		if (mailbox_create(box, update, FALSE) == 0)
+			return 1;
+	}
+	if (mailbox_get_last_mail_error(box) == MAIL_ERROR_EXISTS)
+		return 0;
+	mailbox_set_critical(box,
+		"List rebuild: Couldn't create mailbox %s: %s",
+		mailbox_get_vname(box), mailbox_get_last_internal_error(box, NULL));
+	return -1;
+}
+
+static int
+mail_storage_list_index_try_create(struct mail_storage_list_index_rebuild_ctx *ctx,
+				   struct mailbox_list *list,
+				   const uint8_t *guid_p,
+				   const char *boxname,
+				   bool retry)
+{
+	struct mail_storage *storage = ctx->storage;
+	struct mailbox *box;
+	struct mailbox_update update;
+	string_t *name = t_str_new(128);
+	unsigned char randomness[8];
+	int ret;
+
+	i_zero(&update);
+	guid_128_copy(update.mailbox_guid, guid_p);
+
+	str_append(name, boxname);
+	if (retry) {
+		random_fill(randomness, sizeof(randomness));
+		str_append_c(name, '-');
+		binary_to_hex_append(name, randomness, sizeof(randomness));
+	}
+	/* ignore ACLs to avoid interference */
+	box = mailbox_alloc(list, str_c(name), MAILBOX_FLAG_IGNORE_ACLS);
+	e_debug(box->event, "Mailbox GUID %s exists in storage, but not in list index",
+		guid_128_to_string(guid_p));
+
+	box->corrupted_mailbox_name = TRUE;
+	if ((ret = mail_storage_list_mailbox_create(box, &update)) <= 0)
+		;
+	else if (mailbox_sync(box, MAILBOX_SYNC_FLAG_FORCE_RESYNC) < 0) {
+		mail_storage_set_critical(storage,
+			"List rebuild: Couldn't force resync on created mailbox %s: %s",
+			str_c(name), mailbox_get_last_internal_error(box, NULL));
+		ret = -1;
+	}
+	mailbox_free(&box);
+
+	if (ret < 0)
+		return ret;
+
+	/* open a second time to rename the mailbox to its original name,
+	   ignore ACLs to avoid interference. */
+	box = mailbox_alloc(list, str_c(name), MAILBOX_FLAG_IGNORE_ACLS);
+	e_debug(box->event, "Attempting to recover original name");
+	if (mailbox_open(box) < 0 &&
+	    mailbox_get_last_mail_error(box) != MAIL_ERROR_NOTFOUND) {
+		mail_storage_set_critical(storage,
+			"List rebuild: Couldn't open recovered mailbox %s: %s",
+			str_c(name), mailbox_get_last_internal_error(box, NULL));
+		ret = -1;
+	}
+	mailbox_free(&box);
+	return ret;
+}
+
+static int
+mail_storage_list_index_create(struct mail_storage_list_index_rebuild_ctx *ctx,
+			       struct mailbox_list *list,
+			       const char *boxname,
+			       const uint8_t *guid_p)
+{
+	int i, ret = 0;
+	/* FIXME: we should find out the mailbox's original namespace from the
+	   mailbox index's header. */
+	for (i = 0; i < 100; i++) {
+		T_BEGIN {
+			ret = mail_storage_list_index_try_create(ctx, list, guid_p,
+								 boxname, i > 0);
+		} T_END;
+		if (ret != 0)
+			return ret;
+	}
+	mail_storage_set_critical(ctx->storage,
+		"List rebuild: Failed to create a new mailbox name for GUID %s - "
+		"everything seems to exist?",
+		guid_128_to_string(guid_p));
+	return -1;
+}
+
+struct mailbox_sort_node {
+	struct mailbox_node node;
+	struct mail_storage_list_index_rebuild_mailbox *box;
+};
+
+static int mail_storage_list_index_add_missing(struct mail_storage_list_index_rebuild_ctx *ctx)
+{
+	struct hash_iterate_context *iter;
+	struct mail_storage_list_index_rebuild_mailbox *box;
+	char *key ATTR_UNUSED;
+	struct mailbox_node *_node;
+	unsigned int num_created = 0;
+	char sep = mail_namespaces_get_root_sep(ctx->storage->user->namespaces);
+	int ret = 0;
+
+	iter = hash_table_iterate_init(ctx->mailboxes);
+	/* we need to sort the boxes so that they end up created in right order
+	   in case we have total loss of indexes */
+
+	e_debug(ctx->storage->event, "Sorting mailbox tree");
+	struct mailbox_tree_context *tree =
+		mailbox_tree_init_size(sep, sizeof(struct mailbox_sort_node));
+	while (hash_table_iterate(iter, ctx->mailboxes, &key, &box)) {
+		bool created;
+		const char *name = box->index_name;
+		if (name == NULL)
+			name = get_box_name(ctx, box);
+		const char *vname =
+			t_strconcat(box->list->ns->prefix, name, NULL);
+		_node =	mailbox_tree_get(tree, vname, &created);
+		struct mailbox_sort_node *node =
+			container_of(_node, struct mailbox_sort_node, node);
+		node->box = box;
+	}
+	hash_table_iterate_deinit(&iter);
+
+	mailbox_tree_sort(tree);
+
+	struct mailbox_tree_iterate_context *tree_iter =
+		mailbox_tree_iterate_init(tree, NULL, 0);
+	const char *box_name;
+	e_debug(ctx->storage->event, "Recovering lost mailboxes");
+	while ((_node = mailbox_tree_iterate_next(tree_iter, &box_name)) != NULL) {
+		struct mailbox_sort_node *node =
+			container_of(_node, struct mailbox_sort_node, node);
+		/* skip any intermediate levels that might get created
+		   into the tree  */
+		if (node->box == NULL)
+			continue;
+		/* this node needs to be created */
+		if (node->box->index_name == NULL) {
+			if (mail_storage_list_index_create(ctx, node->box->list,
+							   box_name,
+							   node->box->guid) < 0)
+				ret = -1;
+			else
+				num_created++;
+		}
+	}
+	mailbox_tree_iterate_deinit(&tree_iter);
+	if (num_created > 0) {
+		e_warning(ctx->storage->event,
+			  "Mailbox list rescan found %u lost mailboxes",
+			  num_created);
+	}
+	mailbox_tree_deinit(&tree);
+	return ret;
+}
+
+static int mail_storage_list_index_rebuild_ctx(struct mail_storage_list_index_rebuild_ctx *ctx)
+{
+	struct mail_storage_list_index_rebuild_ns *rebuild_ns;
+
+	array_foreach_modifiable(&ctx->rebuild_namespaces, rebuild_ns) {
+		e_debug(ctx->storage->event,
+			"Rebuilding list index for namespace '%s'",
+			rebuild_ns->ns->prefix);
+		if (mail_storage_list_index_fill_storage_mailboxes(ctx, rebuild_ns->ns->list) < 0)
+			return -1;
+		if (mail_storage_list_index_find_indexed_mailboxes(ctx, rebuild_ns) < 0)
+			return -1;
+	}
+
+	/* finish list syncing before creating mailboxes, because
+	   mailbox_create() will internally try to re-acquire the lock.
+	   (alternatively we could just add the mailbox to the list index
+	   directly, but that's could cause problems as well.) */
+	mail_storage_list_index_rebuild_unlock_lists(ctx);
+	if (mail_storage_list_index_add_missing(ctx) < 0)
+		return -1;
+	return 0;
+}
+
+static int mail_storage_list_index_rebuild_int(struct mail_storage *storage)
+{
+	struct mail_storage_list_index_rebuild_ctx ctx;
+	int ret;
+
+	if (storage->mailboxes_fs == NULL) {
+		storage->rebuild_list_index = FALSE;
+		mail_storage_set_critical(storage,
+					  "BUG: Can't rebuild mailbox list index: "
+					  "Missing mailboxes_fs");
+		return 0;
+	}
+
+	if (storage->rebuilding_list_index)
+		return 0;
+	storage->rebuilding_list_index = TRUE;
+
+	i_zero(&ctx);
+	ctx.storage = storage;
+	ctx.pool = pool_alloconly_create("mailbox list index rebuild", 10240);
+	hash_table_create(&ctx.mailboxes, ctx.pool, 0, str_hash, strcmp);
+
+	/* if no namespaces are found, do nothing */
+	if (!mail_storage_list_index_rebuild_get_namespaces(&ctx)) {
+		hash_table_destroy(&ctx.mailboxes);
+		pool_unref(&ctx.pool);
+		return 0;
+	}
+
+	/* do this operation while keeping mailbox list index locked.
+	   this avoids race conditions between other list rebuilds and also
+	   makes sure that other processes creating/deleting mailboxes can't
+	   cause confusion with race conditions. */
+	struct event_reason *reason =
+		event_reason_begin("storage:mailbox_list_rebuild");
+	if ((ret = mail_storage_list_index_rebuild_lock_lists(&ctx)) == 0)
+		ret = mail_storage_list_index_rebuild_ctx(&ctx);
+	mail_storage_list_index_rebuild_unlock_lists(&ctx);
+	event_reason_end(&reason);
+
+	hash_table_destroy(&ctx.mailboxes);
+	pool_unref(&ctx.pool);
+
+	if (ret == 0)
+		storage->rebuild_list_index = FALSE;
+	storage->rebuilding_list_index = FALSE;
+	return ret;
+}
+
+int mail_storage_list_index_rebuild_and_set_uncorrupted(struct mail_storage *storage)
+{
+	struct mail_namespace *ns;
+	int ret = 0;
+
+	/* If mailbox list index is disabled, stop any attempt already here.
+	   This saves some allocations and iterating all namespaces. */
+	if (!storage->set->mailbox_list_index) {
+		storage->rebuild_list_index = FALSE;
+		return 0;
+	}
+
+	if (mail_storage_list_index_rebuild_int(storage) < 0)
+		return -1;
+	for (ns = storage->user->namespaces; ns != NULL; ns = ns->next) {
+		if (ns->storage != storage || ns->alias_for != NULL)
+			continue;
+		if (mailbox_list_index_set_uncorrupted(ns->list) < 0)
+			ret = -1;
+	}
+	return ret;
+}
+
+int mail_storage_list_index_rebuild(struct mail_storage *storage,
+				    enum mail_storage_list_index_rebuild_reason reason)
+{
+	/* If mailbox list index is disabled, stop any attempt already here. */
+	if (!storage->set->mailbox_list_index) {
+		storage->rebuild_list_index = FALSE;
+		return 0;
+	}
+
+	switch (reason) {
+	case MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_CORRUPTED:
+		e_warning(storage->event,
+			  "Mailbox list index marked corrupted - rescanning");
+		break;
+	case MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_FORCE_RESYNC:
+		e_debug(storage->event,
+			"Mailbox list index rebuild due to force resync");
+		break;
+	case MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_NO_INBOX:
+		e_debug(storage->event,
+			"Mailbox list index rebuild due to no INBOX");
+		break;
+	}
+	return mail_storage_list_index_rebuild_int(storage);
+}
diff --git a/src/lib-storage/list/mailbox-list-delete.c b/src/lib-storage/list/mailbox-list-delete.c
new file mode 100644
index 0000000..ca773ee
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-delete.c
@@ -0,0 +1,489 @@
+/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "hex-binary.h"
+#include "hostpid.h"
+#include "randgen.h"
+#include "sleep.h"
+#include "unlink-directory.h"
+#include "mailbox-list-private.h"
+#include "mailbox-list-delete.h"
+
+#include <stdio.h>
+#include <dirent.h>
+#include <unistd.h>
+
+static int
+mailbox_list_check_root_delete(struct mailbox_list *list, const char *name,
+			       const char *path)
+{
+	const char *root_dir;
+
+	root_dir = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_DIR);
+	if (strcmp(root_dir, path) != 0)
+		return 0;
+
+	if (strcmp(name, "INBOX") == 0 &&
+	    (list->ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE,
+				       "INBOX can't be deleted.");
+		return -1;
+	}
+	mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE,
+			       "Mail storage root can't be deleted.");
+	return -1;
+}
+
+static const char *unique_fname(void)
+{
+	unsigned char randbuf[8];
+
+	random_fill(randbuf, sizeof(randbuf));
+	return t_strdup_printf("%s.%s.%s", my_hostname, my_pid,
+			       binary_to_hex(randbuf, sizeof(randbuf)));
+
+}
+
+int mailbox_list_delete_maildir_via_trash(struct mailbox_list *list,
+					  const char *name,
+					  const char *trash_dir)
+{
+	const char *src, *trash_dest, *error;
+	unsigned int count;
+
+	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &src) <= 0)
+		i_unreached();
+	if (mailbox_list_check_root_delete(list, name, src) < 0)
+		return -1;
+
+	/* rename the mailbox dir to trash dir, which atomically
+	   marks it as being deleted. */
+	count = 0; trash_dest = trash_dir;
+	for (; rename(src, trash_dest) < 0; count++) {
+		if (ENOTFOUND(errno)) {
+			if (trash_dest != trash_dir && count < 5) {
+				/* either the source was just deleted or
+				   the trash dir was deleted. */
+				trash_dest = trash_dir;
+				continue;
+			}
+			mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+				T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+			return -1;
+		}
+		if (errno == EXDEV) {
+			/* can't do this the fast way */
+			return 0;
+		}
+		if (!EDESTDIREXISTS(errno)) {
+			if (mailbox_list_set_error_from_errno(list))
+				return -1;
+			mailbox_list_set_critical(list,
+				"rename(%s, %s) failed: %m", src, trash_dest);
+			return -1;
+		}
+
+		/* trash dir already exists. the reasons for this are:
+
+		   a) another process is in the middle of deleting it
+		   b) previous process crashed and didn't delete it
+		   c) NFS: mailbox was recently deleted, but some connection
+		      still has that mailbox open. the directory contains .nfs*
+		      files that can't be deleted until the mailbox is closed.
+
+		   Because of c) we'll first try to rename the mailbox under
+		   the trash directory and only later try to delete the entire
+		   trash directory. */
+		if (trash_dir == trash_dest) {
+			trash_dest = t_strconcat(trash_dir, "/",
+						 unique_fname(), NULL);
+		} else if (mailbox_list_delete_trash(trash_dest, &error) < 0 &&
+			   (errno != ENOTEMPTY || count >= 5)) {
+			mailbox_list_set_critical(list,
+				"unlink_directory(%s) failed: %s", trash_dest, error);
+			return -1;
+		}
+	}
+
+	if (mailbox_list_delete_trash(trash_dir, &error) < 0 &&
+	    errno != ENOTEMPTY && errno != EBUSY) {
+		mailbox_list_set_critical(list,
+			"unlink_directory(%s) failed: %s", trash_dir, error);
+
+		/* it's already renamed to trash dir, which means it's
+		   deleted as far as the client is concerned. Report
+		   success. */
+	}
+	return 1;
+}
+
+int mailbox_list_delete_mailbox_file(struct mailbox_list *list,
+				     const char *name, const char *path)
+{
+	/* we can simply unlink() the file */
+	if (unlink(path) == 0)
+		return 0;
+	else if (ENOTFOUND(errno)) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+				       T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+		return -1;
+	} else {
+		if (!mailbox_list_set_error_from_errno(list)) {
+			mailbox_list_set_critical(list,
+				"unlink(%s) failed: %m", path);
+		}
+		return -1;
+	}
+}
+
+int mailbox_list_delete_mailbox_nonrecursive(struct mailbox_list *list,
+					     const char *name, const char *path,
+					     bool rmdir_path)
+{
+	DIR *dir;
+	struct dirent *d;
+	string_t *full_path;
+	size_t dir_len;
+	const char *error;
+	bool mailbox_dir, unlinked_something = FALSE;
+	int ret = 0;
+
+	if (mailbox_list_check_root_delete(list, name, path) < 0)
+		return -1;
+
+	dir = opendir(path);
+	if (dir == NULL) {
+		if (errno == ENOENT) {
+			mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+				T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+		} else {
+			if (!mailbox_list_set_error_from_errno(list)) {
+				mailbox_list_set_critical(list,
+					"opendir(%s) failed: %m", path);
+			}
+		}
+		return -1;
+	}
+
+	full_path = t_str_new(256);
+	str_append(full_path, path);
+	str_append_c(full_path, '/');
+	dir_len = str_len(full_path);
+
+	for (errno = 0; (d = readdir(dir)) != NULL; errno = 0) {
+		if (d->d_name[0] == '.') {
+			/* skip . and .. */
+			if (d->d_name[1] == '\0')
+				continue;
+			if (d->d_name[1] == '.' && d->d_name[2] == '\0')
+				continue;
+		}
+
+		mailbox_dir = list->v.is_internal_name != NULL &&
+			list->v.is_internal_name(list, d->d_name);
+
+		str_truncate(full_path, dir_len);
+		str_append(full_path, d->d_name);
+
+		if (mailbox_dir) {
+			if (mailbox_list_delete_trash(str_c(full_path), &error) < 0) {
+				mailbox_list_set_critical(list,
+					"unlink_directory(%s) failed: %s",
+					str_c(full_path), error);
+			} else {
+				unlinked_something = TRUE;
+			}
+			continue;
+		}
+
+		/* trying to unlink() a directory gives either EPERM or EISDIR
+		   (non-POSIX). it doesn't really work anywhere in practise,
+		   so don't bother stat()ing the file first */
+		if (unlink(str_c(full_path)) == 0)
+			unlinked_something = TRUE;
+		else if (errno != ENOENT && !UNLINK_EISDIR(errno)) {
+			mailbox_list_set_critical(list,
+				"unlink(%s) failed: %m", str_c(full_path));
+			ret = -1;
+		} else {
+			/* child directories still exist */
+			rmdir_path = FALSE;
+		}
+	}
+	if (errno != 0) {
+		mailbox_list_set_critical(list, "readdir(%s) failed: %m", path);
+		ret = -1;
+	}
+	if (closedir(dir) < 0) {
+		mailbox_list_set_critical(list, "closedir(%s) failed: %m",
+					  path);
+		ret = -1;
+	}
+	if (ret < 0)
+		return -1;
+
+	if (rmdir_path) {
+		unsigned int try_count = 0;
+		int ret = rmdir(path);
+		while (ret < 0 && errno == ENOTEMPTY && try_count++ < 10) {
+			/* We didn't see any child directories, so this is
+			   either a race condition or .nfs* files were left
+			   lying around. In case it's .nfs* files, retry after
+			   waiting a bit. Hopefully all processes keeping those
+			   files open will have closed them by then. */
+			i_sleep_msecs(100);
+			ret = rmdir(path);
+		}
+		if (rmdir(path) == 0)
+			unlinked_something = TRUE;
+		else if (errno == ENOENT) {
+			/* race condition with another process, which finished
+			   deleting it first. */
+			mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+				T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+		} else if (errno != ENOTEMPTY && errno != EEXIST) {
+			mailbox_list_set_critical(list, "rmdir(%s) failed: %m",
+						  path);
+			return -1;
+		}
+	}
+
+	if (!unlinked_something) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE,
+				       "Mailbox has children, can't delete it");
+		return -1;
+	}
+	return 0;
+}
+
+static bool mailbox_list_path_is_index(struct mailbox_list *list,
+				       enum mailbox_list_path_type type)
+{
+	const char *index_root, *type_root;
+
+	if (type == MAILBOX_LIST_PATH_TYPE_INDEX)
+		return TRUE;
+
+	/* e.g. CONTROL dir could point to the same INDEX dir. */
+	type_root = mailbox_list_get_root_forced(list, type);
+	index_root = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_INDEX);
+	return strcmp(type_root, index_root) == 0;
+}
+
+void mailbox_list_delete_until_root(struct mailbox_list *list, const char *path,
+				    enum mailbox_list_path_type type)
+{
+	const char *root_dir, *p;
+	size_t len;
+
+	if (list->set.iter_from_index_dir && !list->set.no_noselect &&
+	    mailbox_list_path_is_index(list, type)) {
+		/* Don't auto-rmdir parent index directories with ITERINDEX.
+		   Otherwise it'll get us into inconsistent state with a
+		   \NoSelect mailbox in the mail directory but not in index
+		   directory. */
+		return;
+	}
+
+	root_dir = mailbox_list_get_root_forced(list, type);
+	if (!str_begins(path, root_dir)) {
+		/* mbox workaround: name=child/box, root_dir=mail/.imap/,
+		   path=mail/child/.imap/box. we'll want to try to delete
+		   the .imap/ part, but no further. */
+		len = strlen(path);
+		while (len > 0 && path[len-1] != '/')
+			len--;
+		if (len == 0)
+			return;
+		len--;
+		while (len > 0 && path[len-1] != '/')
+			len--;
+		if (len == 0)
+			return;
+
+		root_dir = t_strndup(path, len-1);
+	}
+	while (strcmp(path, root_dir) != 0) {
+		if (rmdir(path) < 0 && errno != ENOENT) {
+			if (errno == ENOTEMPTY || errno == EEXIST)
+				return;
+
+			mailbox_list_set_critical(list, "rmdir(%s) failed: %m",
+						  path);
+			return;
+		}
+		p = strrchr(path, '/');
+		if (p == NULL)
+			break;
+
+		path = t_strdup_until(path, p);
+	}
+}
+
+void mailbox_list_delete_mailbox_until_root(struct mailbox_list *list,
+					    const char *storage_name)
+{
+	enum mailbox_list_path_type types[] = {
+		MAILBOX_LIST_PATH_TYPE_DIR,
+		MAILBOX_LIST_PATH_TYPE_ALT_DIR,
+		MAILBOX_LIST_PATH_TYPE_CONTROL,
+		MAILBOX_LIST_PATH_TYPE_INDEX,
+		MAILBOX_LIST_PATH_TYPE_INDEX_PRIVATE,
+		MAILBOX_LIST_PATH_TYPE_INDEX_CACHE,
+	};
+	const char *path;
+
+	for (unsigned int i = 0; i < N_ELEMENTS(types); i++) {
+		if (mailbox_list_get_path(list, storage_name, types[i], &path) > 0)
+			mailbox_list_delete_until_root(list, path, types[i]);
+	}
+}
+
+static int mailbox_list_try_delete(struct mailbox_list *list, const char *name,
+				   enum mailbox_list_path_type type)
+{
+	const char *mailbox_path, *index_path, *path, *error;
+	int ret;
+
+	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &mailbox_path) <= 0 ||
+	    mailbox_list_get_path(list, name, type, &path) <= 0 ||
+	    strcmp(path, mailbox_path) == 0)
+		return 0;
+
+	if (type == MAILBOX_LIST_PATH_TYPE_CONTROL &&
+	    mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_INDEX,
+				  &index_path) > 0 &&
+	    strcmp(index_path, path) == 0) {
+		/* CONTROL dir is the same as INDEX dir, which we already
+		   deleted. We don't want to continue especially with
+		   iter_from_index_dir=yes, because it could be deleting the
+		   index directory. */
+		return 0;
+	}
+
+	/* Note that only ALT currently uses maildir_name in paths.
+	   INDEX and CONTROL don't. */
+	if (type != MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX ||
+	    *list->set.maildir_name == '\0') {
+		/* this directory may contain also child mailboxes' data.
+		   we don't want to delete that. */
+		bool rmdir_path = *list->set.maildir_name != '\0';
+		if (mailbox_list_delete_mailbox_nonrecursive(list, name, path,
+							     rmdir_path) == 0)
+			ret = 1;
+		else {
+			enum mail_error error =
+				mailbox_list_get_last_mail_error(list);
+			if (error != MAIL_ERROR_NOTFOUND &&
+			    error != MAIL_ERROR_NOTPOSSIBLE)
+				return -1;
+			ret = 0;
+		}
+	} else {
+		if (mailbox_list_delete_trash(path, &error) == 0)
+			ret = 1;
+		else if (errno == ENOTEMPTY)
+			ret = 0;
+		else {
+			mailbox_list_set_critical(list,
+				"unlink_directory(%s) failed: %s", path, error);
+			return -1;
+		}
+	}
+
+	/* Avoid leaving empty parent directories lying around.
+	   These parent directories' existence or removal doesn't
+	   affect our return value. */
+	mailbox_list_delete_until_root(list, path, type);
+	return ret;
+}
+
+int mailbox_list_delete_finish(struct mailbox_list *list, const char *name)
+{
+	int ret, ret2;
+
+	ret = mailbox_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_INDEX);
+	ret2 = mailbox_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_INDEX_CACHE);
+	if (ret == 0 || ret2 < 0)
+		ret = ret2;
+	ret2 = mailbox_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_CONTROL);
+	if (ret == 0 || ret2 < 0)
+		ret = ret2;
+	ret2 = mailbox_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX);
+	if (ret == 0 || ret2 < 0)
+		ret = ret2;
+	return ret;
+}
+
+int mailbox_list_delete_finish_ret(struct mailbox_list *list,
+				   const char *name, bool root_delete_success)
+{
+	int ret2;
+
+	if (!root_delete_success &&
+	    mailbox_list_get_last_mail_error(list) != MAIL_ERROR_NOTFOUND) {
+		/* unexpected error - preserve it */
+		return -1;
+	} else if ((ret2 = mailbox_list_delete_finish(list, name)) < 0) {
+		/* unexpected error */
+		return -1;
+	} else if (ret2 > 0) {
+		/* successfully deleted */
+		return 0;
+	} else if (root_delete_success) {
+		/* nothing deleted by us, but root was successfully deleted */
+		return 0;
+	} else {
+		/* nothing deleted by us and the root didn't exist either.
+		   make sure the list has the correct error set, since it
+		   could have been changed. */
+		mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+			T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+		return -1;
+	}
+}
+
+int mailbox_list_delete_trash(const char *path, const char **error_r)
+{
+	if (unlink_directory(path, UNLINK_DIRECTORY_FLAG_RMDIR, error_r) < 0) {
+		if (errno == ELOOP) {
+			/* it's a symlink? try just deleting it */
+			if (unlink(path) == 0)
+				return 0;
+			errno = ELOOP;
+			return -1;
+		}
+		return -1;
+	}
+	return 0;
+}
+
+int mailbox_list_delete_symlink_default(struct mailbox_list *list,
+					const char *name)
+{
+	const char *path;
+	int ret;
+
+	ret = mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_DIR,
+				    &path);
+	if (ret < 0)
+		return -1;
+	i_assert(ret > 0);
+
+	if (unlink(path) == 0)
+		return 0;
+
+	if (errno == ENOENT) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+			T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+	} else if (UNLINK_EISDIR(errno)) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE,
+				       "Mailbox isn't a symlink");
+	} else {
+		mailbox_list_set_critical(list, "unlink(%s) failed: %m", path);
+	}
+	return -1;
+}
diff --git a/src/lib-storage/list/mailbox-list-delete.h b/src/lib-storage/list/mailbox-list-delete.h
new file mode 100644
index 0000000..9b46638
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-delete.h
@@ -0,0 +1,86 @@
+#ifndef MAILBOX_LIST_DELETE_H
+#define MAILBOX_LIST_DELETE_H
+
+#include "mailbox-list.h"
+
+/* Delete the mailbox atomically by rename()ing it to trash_dir and afterwards
+   recursively deleting the trash_dir. If the rename() fails because trash_dir
+   already exists, the trash_dir is first deleted and rename() is retried.
+
+   Returns 1 if the rename() succeeded. Returns 0 if rename() fails with EXDEV,
+   which means the source and destination are on different filesystems and
+   the rename can never succeeed.
+
+   If the path didn't exist, returns -1 and sets the list error to
+   MAIL_ERROR_NOTFOUND.
+
+   Attempting to delete INBOX or the namespace root returns -1 and sets the
+   list error to MAIL_ERROR_NOTPOSSIBLE.
+
+   Returns -1 and sets the list error on other errors. */
+int mailbox_list_delete_maildir_via_trash(struct mailbox_list *list,
+					  const char *name,
+					  const char *trash_dir);
+/* Try to unlink() the path. Returns 0 on success. If the path didn't exist,
+   returns -1 and sets the list error to MAIL_ERROR_NOTFOUND.
+   Returns -1 and sets the list error on other errors. */
+int mailbox_list_delete_mailbox_file(struct mailbox_list *list,
+				     const char *name, const char *path);
+/* Delete all files from the given path. Also all internal directories
+   (as returned by is_internal_name() check) are recursively deleted.
+   Otherwise directories are left undeleted.
+
+   Returns 0 if anything was unlink()ed and no unexpected errors happened.
+   Also returns 0 if there were no files and the path was successfully
+   rmdir()ed.
+
+   If the path didn't exist, returns -1 and sets the list error to
+   MAIL_ERROR_NOTFOUND.
+
+   If the path exists and has subdirectories, but no files were unlink()ed,
+   returns -1 and sets the list error to MAIL_ERROR_NOTPOSSIBLE.
+
+   Attempting to delete INBOX or the namespace root returns -1 and sets the
+   list error to MAIL_ERROR_NOTPOSSIBLE.
+
+   Returns -1 and sets the list error on other errors. */
+int mailbox_list_delete_mailbox_nonrecursive(struct mailbox_list *list,
+					     const char *name, const char *path,
+					     bool rmdir_path);
+/* Lookup INDEX, CONTROL and ALT directories for the mailbox and delete them.
+   Returns 1 if anything was unlink()ed or rmdir()ed, 0 if not.
+   Returns -1 and sets the list error on any errors. */
+int mailbox_list_delete_finish(struct mailbox_list *list, const char *name);
+/* Finish mailbox deletion by calling mailbox_list_delete_finish() if needed.
+   Set root_delete_success to TRUE if the mail root directory was successfully
+   deleted, FALSE if not. The list is expected to have a proper error when
+   root_delete_success==FALSE.
+
+   Returns 0 if mailbox deletion should be treated as success. If not, returns
+   -1 and sets the list error if necessary. */
+int mailbox_list_delete_finish_ret(struct mailbox_list *list,
+				   const char *name, bool root_delete_success);
+
+/* rmdir() path and its parent directories until the root directory is reached.
+   The root isn't rmdir()ed. */
+void mailbox_list_delete_until_root(struct mailbox_list *list, const char *path,
+				    enum mailbox_list_path_type type);
+/* Call mailbox_list_delete_until_root() for all the paths of the mailbox. */
+void mailbox_list_delete_mailbox_until_root(struct mailbox_list *list,
+					    const char *storage_name);
+/* Wrapper to unlink_directory(UNLINK_DIRECTORY_FLAG_RMDIR). If it fails due
+   to ELOOP, try to unlink() the path instead. */
+int mailbox_list_delete_trash(const char *path, const char **error_r);
+/* Try to unlink() the path to the mailbox. Returns 0 on success.
+
+   If the path didn't exist, returns -1 and sets the list error to
+   MAIL_ERROR_NOTFOUND.
+
+   If the path is a directory, returns -1 and sets the list error to
+   MAIL_ERROR_NOTPOSSIBLE.
+
+   Returns -1 and sets the list error on other errors. */
+int mailbox_list_delete_symlink_default(struct mailbox_list *list,
+					const char *name);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-fs-flags.c b/src/lib-storage/list/mailbox-list-fs-flags.c
new file mode 100644
index 0000000..3f3bd94
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-fs-flags.c
@@ -0,0 +1,243 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "mailbox-list-fs.h"
+
+#include <sys/stat.h>
+
+/* Assume that if atime < mtime, there are new mails. If it's good enough for
+   UW-IMAP, it's good enough for us. */
+#define STAT_GET_MARKED_FILE(st) \
+	((st).st_size == 0 ? MAILBOX_UNMARKED : \
+	 (st).st_atime < (st).st_mtime ? MAILBOX_MARKED : MAILBOX_UNMARKED)
+
+static int
+list_is_maildir_mailbox(struct mailbox_list *list, const char *dir,
+			const char *fname, enum mailbox_list_file_type type,
+			enum mailbox_info_flags *flags_r)
+{
+	const char *path, *maildir_path;
+	struct stat st, st2;
+	bool mailbox_files;
+
+	switch (type) {
+	case MAILBOX_LIST_FILE_TYPE_FILE:
+	case MAILBOX_LIST_FILE_TYPE_OTHER:
+		/* non-directories aren't valid */
+		*flags_r |= MAILBOX_NOSELECT | MAILBOX_NOINFERIORS;
+		return 0;
+
+	case MAILBOX_LIST_FILE_TYPE_DIR:
+	case MAILBOX_LIST_FILE_TYPE_UNKNOWN:
+	case MAILBOX_LIST_FILE_TYPE_SYMLINK:
+		break;
+	}
+
+	path = t_strdup_printf("%s/%s", dir, fname);
+	if (stat(path, &st) < 0) {
+		if (errno == ENOENT) {
+			*flags_r |= MAILBOX_NONEXISTENT;
+			return 0;
+		} else {
+			/* non-selectable. probably either access denied, or
+			   symlink destination not found. don't bother logging
+			   errors. */
+			*flags_r |= MAILBOX_NOSELECT;
+			return 1;
+		}
+	}
+	if (!S_ISDIR(st.st_mode)) {
+		if (str_begins(fname, ".nfs")) {
+			/* temporary NFS file */
+			*flags_r |= MAILBOX_NONEXISTENT;
+		} else {
+			*flags_r |= MAILBOX_NOSELECT | MAILBOX_NOINFERIORS;
+		}
+		return 0;
+	}
+
+	/* ok, we've got a directory. see what we can do about it. */
+
+	/* 1st link is "."
+	   2nd link is ".."
+	   3rd link is either child mailbox or mailbox dir
+	   rest of the links are child mailboxes
+
+	   if mailboxes are files, then 3+ links are all child mailboxes.
+	*/
+	mailbox_files = (list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0;
+	if (st.st_nlink == 2 && !mailbox_files) {
+		*flags_r |= MAILBOX_NOSELECT;
+		return 1;
+	}
+
+	/* we have at least one directory. see if this mailbox is selectable */
+	maildir_path = t_strconcat(path, "/", list->set.maildir_name, NULL);
+	if (stat(maildir_path, &st2) < 0)
+		*flags_r |= MAILBOX_NOSELECT | MAILBOX_CHILDREN;
+	else if (!S_ISDIR(st2.st_mode)) {
+		if (mailbox_files) {
+			*flags_r |= st.st_nlink == 2 ?
+				MAILBOX_NOCHILDREN : MAILBOX_CHILDREN;
+		} else {
+			*flags_r |= MAILBOX_NOSELECT | MAILBOX_CHILDREN;
+		}
+	} else {
+		/* now we know what link count 3 means. */
+		if (st.st_nlink == 3)
+			*flags_r |= MAILBOX_NOCHILDREN;
+		else
+			*flags_r |= MAILBOX_CHILDREN;
+	}
+	*flags_r |= MAILBOX_SELECT;
+	return 1;
+}
+
+static bool
+is_inbox_file(struct mailbox_list *list, const char *path, const char *fname)
+{
+	const char *inbox_path;
+
+	if (strcasecmp(fname, "INBOX") != 0)
+		return FALSE;
+
+	if (mailbox_list_get_path(list, "INBOX",
+				  MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &inbox_path) <= 0)
+		i_unreached();
+	return strcmp(inbox_path, path) == 0;
+}
+
+int fs_list_get_mailbox_flags(struct mailbox_list *list,
+			      const char *dir, const char *fname,
+			      enum mailbox_list_file_type type,
+			      enum mailbox_info_flags *flags_r)
+{
+	struct stat st;
+	const char *path;
+
+	*flags_r = 0;
+
+	if (*list->set.maildir_name != '\0' && !list->set.iter_from_index_dir) {
+		/* maildir_name is set: This is the simple case that works for
+		   all mail storage formats, because the only thing that
+		   matters for existence or child checks is whether the
+		   maildir_name exists or not. For example with Maildir this
+		   doesn't care whether the "cur" directory exists; as long
+		   as the parent maildir_name exists, the Maildir is
+		   selectable. */
+		return list_is_maildir_mailbox(list, dir, fname, type, flags_r);
+	}
+	/* maildir_name is not set: Now we (may) need to use storage-specific
+	   code to determine whether the mailbox is selectable or if it has
+	   children.
+
+	   We're here also when iterating from index directory, because even
+	   though maildir_name is set, it's not used for index directory.
+	*/
+
+	if (!list->set.iter_from_index_dir &&
+	    list->v.is_internal_name != NULL &&
+	    list->v.is_internal_name(list, fname)) {
+		/* skip internal dirs. For example Maildir's cur/new/tmp */
+		*flags_r |= MAILBOX_NOSELECT;
+		return 0;
+	}
+
+	switch (type) {
+	case MAILBOX_LIST_FILE_TYPE_DIR:
+		/* We know that we're looking at a directory. If the storage
+		   uses files, it has to be a \NoSelect directory. */
+		if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+			*flags_r |= MAILBOX_NOSELECT;
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_FILE_TYPE_FILE:
+		/* We know that we're looking at a file. If the storage
+		   doesn't use files, it's not a mailbox and we want to skip
+		   it. */
+		if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0) {
+			*flags_r |= MAILBOX_NOSELECT | MAILBOX_NOINFERIORS;
+			return 0;
+		}
+		break;
+	default:
+		break;
+	}
+
+	/* we've done all filtering we can before stat()ing */
+	path = t_strconcat(dir, "/", fname, NULL);
+	if (stat(path, &st) < 0) {
+		if (ENOTFOUND(errno)) {
+			*flags_r |= MAILBOX_NONEXISTENT;
+			return 0;
+		} else if (ENOACCESS(errno)) {
+			*flags_r |= MAILBOX_NOSELECT;
+			return 1;
+		} else {
+			/* non-selectable. probably either access denied, or
+			   symlink destination not found. don't bother logging
+			   errors. */
+			mailbox_list_set_critical(list, "stat(%s) failed: %m",
+						  path);
+			return -1;
+		}
+	}
+
+	if (!S_ISDIR(st.st_mode)) {
+		if (str_begins(fname, ".nfs")) {
+			/* temporary NFS file */
+			*flags_r |= MAILBOX_NONEXISTENT;
+			return 0;
+		}
+
+		if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0) {
+			*flags_r |= MAILBOX_NOSELECT | MAILBOX_NOINFERIORS;
+			return 0;
+		}
+		/* looks like a valid mailbox file */
+		if (is_inbox_file(list, path, fname) &&
+		    strcmp(fname, "INBOX") != 0) {
+			/* it's possible for INBOX to have child
+			   mailboxes as long as the inbox file itself
+			   isn't in <mail root>/INBOX */
+		} else {
+			*flags_r |= MAILBOX_NOINFERIORS;
+		}
+		/* Return mailbox files as always existing. The current
+		   mailbox_exists() code would do the same stat() anyway
+		   without further checks, so might as well avoid the second
+		   stat(). */
+		*flags_r |= MAILBOX_SELECT;
+		*flags_r |= STAT_GET_MARKED_FILE(st);
+		return 1;
+	}
+
+	/* This is a directory */
+	if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+		/* We should get here only if type is
+		   MAILBOX_LIST_FILE_TYPE_UNKNOWN because the filesystem didn't
+		   return the type. Normally this should have already been
+		   handled by the MAILBOX_LIST_FILE_TYPE_DIR check above. */
+		*flags_r |= MAILBOX_NOSELECT;
+		return 1;
+	}
+
+	if (list->v.is_internal_name == NULL || list->set.iter_from_index_dir) {
+		/* This mailbox format doesn't use any special directories
+		   (e.g. Maildir's cur/new/tmp). In that case we can look at
+		   the directory's link count to determine whether there are
+		   children or not. The directory's link count equals the
+		   number of subdirectories it has. The first two links are
+		   for "." and "..".
+
+		   link count < 2 can happen with filesystems that don't
+		   support link counts. we'll just ignore them for now.. */
+		if (st.st_nlink == 2)
+			*flags_r |= MAILBOX_NOCHILDREN;
+		else if (st.st_nlink > 2)
+			*flags_r |= MAILBOX_CHILDREN;
+	}
+	return 1;
+}
diff --git a/src/lib-storage/list/mailbox-list-fs-iter.c b/src/lib-storage/list/mailbox-list-fs-iter.c
new file mode 100644
index 0000000..b95aabc
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-fs-iter.c
@@ -0,0 +1,833 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "str.h"
+#include "unichar.h"
+#include "imap-match.h"
+#include "imap-utf7.h"
+#include "mail-storage.h"
+#include "mailbox-tree.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-iter-private.h"
+#include "mailbox-list-fs.h"
+
+#include <stdio.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <sys/stat.h>
+
+struct list_dir_entry {
+	const char *fname;
+	enum mailbox_info_flags info_flags;
+};
+
+struct list_dir_context {
+	struct list_dir_context *parent;
+
+	pool_t pool;
+	const char *storage_name;
+	/* this directory's info flags. */
+	enum mailbox_info_flags info_flags;
+
+	/* all files in this directory */
+	ARRAY(struct list_dir_entry) entries;
+	unsigned int entry_idx;
+};
+
+struct fs_list_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+
+	const char *const *valid_patterns;
+	/* roots can be either /foo, ~user/bar or baz */
+	ARRAY(const char *) roots;
+	unsigned int root_idx;
+	char sep;
+
+	pool_t info_pool;
+	struct mailbox_info info;
+	/* current directory we're handling */
+	struct list_dir_context *dir;
+
+	bool inbox_found:1;
+	bool inbox_has_children:1;
+	bool listed_prefix_inbox:1;
+};
+
+static int
+fs_get_existence_info_flag(struct fs_list_iterate_context *ctx,
+			   const char *vname,
+			   enum mailbox_info_flags *info_flags)
+{
+	struct mailbox *box;
+	enum mailbox_flags flags = 0;
+	enum mailbox_existence existence;
+	bool auto_boxes;
+	int ret;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_RAW_LIST) != 0)
+		flags |= MAILBOX_FLAG_IGNORE_ACLS;
+	auto_boxes = (ctx->ctx.flags & MAILBOX_LIST_ITER_NO_AUTO_BOXES) == 0;
+	box = mailbox_alloc(ctx->ctx.list, vname, flags);
+	ret = mailbox_exists(box, auto_boxes, &existence);
+	mailbox_free(&box);
+
+	if (ret < 0) {
+		/* this can only be an internal error */
+		mailbox_list_set_internal_error(ctx->ctx.list);
+		return -1;
+	}
+	switch (existence) {
+	case MAILBOX_EXISTENCE_NONE:
+		/* We already found out that this mailbox exists. So this is
+		   either a race condition or ACL plugin prevented access to
+		   this. In any case treat this as a \NoSelect mailbox so that
+		   we'll recurse into its potential children. This is
+		   especially important if ACL disabled access to the parent
+		   mailbox, but child mailboxes would be accessible. */
+	case MAILBOX_EXISTENCE_NOSELECT:
+		*info_flags |= MAILBOX_NOSELECT;
+		break;
+	case MAILBOX_EXISTENCE_SELECT:
+		*info_flags |= MAILBOX_SELECT;
+		break;
+	}
+	return 0;
+}
+
+static void
+fs_list_rename_invalid(struct fs_list_iterate_context *ctx,
+		       const char *storage_name)
+{
+	/* the storage_name is completely invalid, rename it to
+	   something more sensible. we could do this for all names that
+	   aren't valid mUTF-7, but that might lead to accidents in
+	   future when UTF-8 storage names are used */
+	string_t *destname = t_str_new(128);
+	string_t *dest = t_str_new(128);
+	const char *root, *src;
+
+	root = mailbox_list_get_root_forced(ctx->ctx.list,
+					  MAILBOX_LIST_PATH_TYPE_MAILBOX);
+	src = t_strconcat(root, "/", storage_name, NULL);
+
+	if (uni_utf8_get_valid_data((const void *)storage_name,
+				    strlen(storage_name), destname))
+		i_unreached(); /* already checked that it was invalid */
+
+	str_append(dest, root);
+	str_append_c(dest, '/');
+	(void)imap_utf8_to_utf7(str_c(destname), dest);
+
+	if (rename(src, str_c(dest)) < 0 && errno != ENOENT)
+		e_error(ctx->ctx.list->ns->user->event,
+			"rename(%s, %s) failed: %m", src, str_c(dest));
+}
+
+static const char *
+dir_get_storage_name(struct list_dir_context *dir, const char *fname)
+{
+	if (*dir->storage_name == '\0') {
+		/* regular root */
+		return fname;
+	} else if (strcmp(dir->storage_name, "/") == 0) {
+		/* full_filesystem_access=yes "/" root */
+		return t_strconcat("/", fname, NULL);
+	} else {
+		/* child */
+		return *fname == '\0' ? dir->storage_name :
+			t_strconcat(dir->storage_name, "/", fname, NULL);
+	}
+}
+
+static int
+dir_entry_get(struct fs_list_iterate_context *ctx, const char *dir_path,
+	      struct list_dir_context *dir, const struct dirent *d)
+{
+	const char *storage_name, *vname, *root_dir;
+	struct list_dir_entry *entry;
+	enum imap_match_result match;
+	enum mailbox_info_flags info_flags;
+	int ret;
+
+	/* skip . and .. */
+	if (d->d_name[0] == '.' &&
+	    (d->d_name[1] == '\0' ||
+	     (d->d_name[1] == '.' && d->d_name[2] == '\0')))
+		return 0;
+
+	if (strcmp(d->d_name, ctx->ctx.list->set.maildir_name) == 0) {
+		/* mail storage's internal directory (e.g. dbox-Mails).
+		   this also means that the parent is selectable */
+		dir->info_flags &= ENUM_NEGATE(MAILBOX_NOSELECT);
+		dir->info_flags |= MAILBOX_SELECT;
+		return 0;
+	}
+	if (ctx->ctx.list->set.subscription_fname != NULL &&
+	    strcmp(d->d_name, ctx->ctx.list->set.subscription_fname) == 0) {
+		/* if this is the subscriptions file, skip it */
+		root_dir = mailbox_list_get_root_forced(ctx->ctx.list,
+							MAILBOX_LIST_PATH_TYPE_DIR);
+		if (strcmp(root_dir, dir_path) == 0)
+			return 0;
+	}
+
+	/* check the pattern */
+	storage_name = dir_get_storage_name(dir, d->d_name);
+	vname = mailbox_list_get_vname(ctx->ctx.list, storage_name);
+	if (!uni_utf8_str_is_valid(vname)) {
+		fs_list_rename_invalid(ctx, storage_name);
+		/* just skip this in this iteration, we'll see it on the
+		   next list */
+		return 0;
+	}
+
+	match = imap_match(ctx->ctx.glob, vname);
+	if (strcmp(d->d_name, "INBOX") == 0 && strcmp(vname, "INBOX") == 0 &&
+	    ctx->ctx.list->ns->prefix_len > 0) {
+		/* The glob was matched only against "INBOX", but this
+		   directory may hold also prefix/INBOX. Just assume here
+		   that it matches and verify later whether it was needed
+		   or not. */
+		match = IMAP_MATCH_YES;
+	}
+
+	if ((dir->info_flags & (MAILBOX_CHILDREN | MAILBOX_NOCHILDREN |
+				MAILBOX_NOINFERIORS)) == 0 &&
+	    (ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_CHILDREN) != 0) {
+		/* we don't know yet if the parent has children. need to figure
+		   out if this file is actually a visible mailbox */
+	} else if (match != IMAP_MATCH_YES &&
+		   (match & IMAP_MATCH_CHILDREN) == 0) {
+		/* mailbox doesn't match any patterns, we don't care about it */
+		return 0;
+	}
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SKIP_ALIASES) != 0) {
+		ret = mailbox_list_dirent_is_alias_symlink(ctx->ctx.list,
+							   dir_path, d);
+		if (ret != 0)
+			return ret < 0 ? -1 : 0;
+	}
+	ret = ctx->ctx.list->v.
+		get_mailbox_flags(ctx->ctx.list, dir_path, d->d_name,
+				  mailbox_list_get_file_type(d), &info_flags);
+	if (ret <= 0)
+		return ret;
+	if (!MAILBOX_INFO_FLAGS_FINISHED(info_flags)) {
+		/* mailbox existence isn't known yet. need to figure it out
+		   the hard way. */
+		if (fs_get_existence_info_flag(ctx, vname, &info_flags) < 0)
+			return -1;
+	}
+	if ((info_flags & MAILBOX_NONEXISTENT) != 0)
+		return 0;
+
+	/* mailbox exists - make sure parent knows it has children */
+	dir->info_flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN | MAILBOX_NOINFERIORS);
+	dir->info_flags |= MAILBOX_CHILDREN;
+
+	if (match != IMAP_MATCH_YES && (match & IMAP_MATCH_CHILDREN) == 0) {
+		/* this mailbox didn't actually match any pattern,
+		   we just needed to know the children state */
+		return 0;
+	}
+
+	/* entry matched a pattern. we're going to return this. */
+	entry = array_append_space(&dir->entries);
+	entry->fname = p_strdup(dir->pool, d->d_name);
+	entry->info_flags = info_flags;
+	return 0;
+}
+
+static bool
+fs_list_get_storage_path(struct fs_list_iterate_context *ctx,
+			 const char *storage_name, const char **path_r)
+{
+	const char *root, *path = storage_name;
+
+	if (*path == '~') {
+		if (!mailbox_list_try_get_absolute_path(ctx->ctx.list, &path)) {
+			/* a) couldn't expand ~user/
+			   b) mailbox is under our mail root, we changed
+			   path to storage_name */
+		}
+		/* NOTE: the path may have been translated to a storage_name
+		   instead of path */
+	}
+	if (*path != '/') {
+		/* non-absolute path. add the mailbox root dir as prefix. */
+		enum mailbox_list_path_type type =
+			ctx->ctx.list->set.iter_from_index_dir ?
+			MAILBOX_LIST_PATH_TYPE_INDEX :
+			MAILBOX_LIST_PATH_TYPE_MAILBOX;
+		if (!mailbox_list_get_root_path(ctx->ctx.list, type, &root))
+			return FALSE;
+		if (ctx->ctx.list->set.iter_from_index_dir &&
+		    ctx->ctx.list->set.mailbox_dir_name[0] != '\0') {
+			/* append "mailboxes/" to the index root */
+			root = t_strconcat(root, "/",
+				ctx->ctx.list->set.mailbox_dir_name, NULL);
+		}
+		path = *path == '\0' ? root :
+			t_strconcat(root, "/", path, NULL);
+	}
+	*path_r = path;
+	return TRUE;
+}
+
+static int
+fs_list_dir_read(struct fs_list_iterate_context *ctx,
+		 struct list_dir_context *dir)
+{
+	DIR *fsdir;
+	struct dirent *d;
+	const char *path;
+	int ret = 0;
+
+	if (!fs_list_get_storage_path(ctx, dir->storage_name, &path))
+		return 0;
+	if (path == NULL) {
+		/* no mailbox root dir */
+		return 0;
+	}
+
+	fsdir = opendir(path);
+	if (fsdir == NULL) {
+		if (ENOTFOUND(errno)) {
+			/* root) user gave invalid hierarchy, ignore
+			   sub) probably just race condition with other client
+			   deleting the mailbox. */
+			return 0;
+		}
+		if (errno == EACCES) {
+			/* ignore permission errors */
+			return 0;
+		}
+		mailbox_list_set_critical(ctx->ctx.list,
+					  "opendir(%s) failed: %m", path);
+		return -1;
+	}
+	if ((dir->info_flags & (MAILBOX_SELECT | MAILBOX_NOSELECT)) == 0) {
+		/* we don't know if the parent is selectable or not. start with
+		   the assumption that it isn't, until we see maildir_name */
+		dir->info_flags |= MAILBOX_NOSELECT;
+	}
+
+	errno = 0;
+	while ((d = readdir(fsdir)) != NULL) T_BEGIN {
+		if (dir_entry_get(ctx, path, dir, d) < 0)
+			ret = -1;
+		errno = 0;
+	} T_END;
+	if (errno != 0) {
+		mailbox_list_set_critical(ctx->ctx.list,
+			"readdir(%s) failed: %m", path);
+		ret = -1;
+	}
+	if (closedir(fsdir) < 0) {
+		mailbox_list_set_critical(ctx->ctx.list,
+			"closedir(%s) failed: %m", path);
+		ret = -1;
+	}
+	return ret;
+}
+
+static struct list_dir_context *
+fs_list_read_dir(struct fs_list_iterate_context *ctx, const char *storage_name,
+		 enum mailbox_info_flags info_flags)
+{
+	struct list_dir_context *dir;
+	pool_t pool;
+
+	pool = pool_alloconly_create(MEMPOOL_GROWING"fs iter dir", 256);
+	dir = p_new(pool, struct list_dir_context, 1);
+	dir->pool = pool;
+	dir->storage_name = p_strdup(pool, storage_name);
+	dir->info_flags = info_flags;
+	p_array_init(&dir->entries, pool, 16);
+
+	if (fs_list_dir_read(ctx, dir) < 0)
+		ctx->ctx.failed = TRUE;
+
+	if ((dir->info_flags & (MAILBOX_CHILDREN | MAILBOX_NOCHILDREN |
+				MAILBOX_NOINFERIORS)) == 0) {
+		/* assume this directory has no children */
+		dir->info_flags |= MAILBOX_NOCHILDREN;
+	}
+	return dir;
+}
+
+static bool
+fs_list_get_valid_patterns(struct fs_list_iterate_context *ctx,
+			   const char *const *patterns)
+{
+	struct mailbox_list *_list = ctx->ctx.list;
+	ARRAY(const char *) valid_patterns;
+	const char *pattern, *test_pattern, *real_pattern, *error;
+	size_t prefix_len;
+
+	prefix_len = strlen(_list->ns->prefix);
+	p_array_init(&valid_patterns, ctx->ctx.pool, 8);
+	for (; *patterns != NULL; patterns++) {
+		/* check that we're not trying to do any "../../" lists */
+		test_pattern = *patterns;
+		/* skip namespace prefix if possible. this allows using
+		   e.g. ~/mail/ prefix and have it pass the pattern
+		   validation. */
+		if (strncmp(test_pattern, _list->ns->prefix, prefix_len) == 0)
+			test_pattern += prefix_len;
+		if (!uni_utf8_str_is_valid(test_pattern)) {
+			/* ignore invalid UTF8 patterns */
+			continue;
+		}
+		/* check pattern also when it's converted to use real
+		   separators. */
+		real_pattern =
+			mailbox_list_get_storage_name(_list, test_pattern);
+		if (mailbox_list_is_valid_name(_list, test_pattern, &error) &&
+		    mailbox_list_is_valid_name(_list, real_pattern, &error)) {
+			pattern = p_strdup(ctx->ctx.pool, *patterns);
+			array_push_back(&valid_patterns, &pattern);
+		}
+	}
+	array_append_zero(&valid_patterns); /* NULL-terminate */
+	ctx->valid_patterns = array_front(&valid_patterns);
+
+	return array_count(&valid_patterns) > 1;
+}
+
+static void fs_list_get_roots(struct fs_list_iterate_context *ctx)
+{
+	struct mail_namespace *ns = ctx->ctx.list->ns;
+	char ns_sep = mail_namespace_get_sep(ns);
+	bool full_fs_access =
+		ctx->ctx.list->mail_set->mail_full_filesystem_access;
+	const char *const *patterns, *pattern, *parent, *child;
+	const char *p, *last, *root, *prefix_vname;
+	unsigned int i;
+	size_t parentlen;
+
+	i_assert(*ctx->valid_patterns != NULL);
+
+	/* get the root dirs for all the patterns */
+	p_array_init(&ctx->roots, ctx->ctx.pool, 8);
+	for (patterns = ctx->valid_patterns; *patterns != NULL; patterns++) {
+		pattern = *patterns;
+
+		if (strncmp(pattern, ns->prefix, ns->prefix_len) != 0) {
+			/* typically e.g. prefix=foo/bar/, pattern=foo/%/%
+			   we'll use root="" for this.
+
+			   it might of course also be pattern=foo/%/prefix/%
+			   where we could optimize with root=prefix, but
+			   probably too much trouble to implement. */
+			prefix_vname = "";
+		} else {
+			for (p = last = pattern; *p != '\0'; p++) {
+				if (*p == '%' || *p == '*')
+					break;
+				if (*p == ns_sep)
+					last = p;
+			}
+			prefix_vname = t_strdup_until(pattern, last);
+		}
+
+		if (*pattern == ns_sep && full_fs_access) {
+			/* pattern=/something with full filesystem access.
+			   (without full filesystem access we want to skip this
+			   if namespace prefix begins with separator) */
+			root = "/";
+		} else if ((ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0 &&
+			 ns->prefix_len == 6 &&
+			 strcasecmp(prefix_vname, "INBOX") == 0 &&
+			 strncasecmp(ns->prefix, pattern, ns->prefix_len) == 0) {
+			/* special case: Namespace prefix is INBOX/ and
+			   we just want to see its contents (not the
+			   INBOX's children). */
+			root = "";
+		} else if ((ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0 &&
+			   ns->type == MAIL_NAMESPACE_TYPE_SHARED &&
+			   !ctx->ctx.list->mail_set->mail_shared_explicit_inbox &&
+			   (prefix_vname[0] == '\0' ||
+			    (strncmp(ns->prefix, prefix_vname, ns->prefix_len-1) == 0 &&
+			     prefix_vname[ns->prefix_len-1] == '\0'))) {
+			/* we need to handle ns prefix explicitly here, because
+			   getting storage name with
+			   mail_shared_explicit_inbox=no would return
+			   root=INBOX. (e.g. LIST "" shared/user/box has to
+			   return the box when it doesn't exist but
+			   shared/user/box/child exists) */
+			root = "";
+		} else {
+			root = mailbox_list_get_storage_name(ctx->ctx.list,
+							     prefix_vname);
+		}
+
+		if (*root == '/') {
+			/* /absolute/path */
+			i_assert(full_fs_access);
+		} else if (*root == '~') {
+			/* ~user/path - don't expand the ~user/ path, since we
+			   need to be able to convert the path back to vname */
+			i_assert(full_fs_access);
+		} else {
+			/* mailbox name */
+		}
+		root = p_strdup(ctx->ctx.pool, root);
+		array_push_back(&ctx->roots, &root);
+	}
+	/* sort the root dirs so that /foo is before /foo/bar */
+	array_sort(&ctx->roots, i_strcmp_p);
+	/* remove /foo/bar when there already exists /foo parent */
+	for (i = 1; i < array_count(&ctx->roots); ) {
+		parent = array_idx_elem(&ctx->roots, i-1);
+		child = array_idx_elem(&ctx->roots, i);
+		parentlen = strlen(parent);
+		if (str_begins(child, parent) &&
+		    (parentlen == 0 ||
+		     child[parentlen] == ctx->sep ||
+		     child[parentlen] == '\0'))
+			array_delete(&ctx->roots, i, 1);
+		else
+			i++;
+	}
+}
+
+static void fs_list_next_root(struct fs_list_iterate_context *ctx)
+{
+	const char *const *roots;
+	unsigned int count;
+
+	i_assert(ctx->dir == NULL);
+
+	roots = array_get(&ctx->roots, &count);
+	if (ctx->root_idx == count)
+		return;
+	ctx->dir = fs_list_read_dir(ctx, roots[ctx->root_idx],
+				    MAILBOX_NOSELECT);
+	ctx->root_idx++;
+}
+
+struct mailbox_list_iterate_context *
+fs_list_iter_init(struct mailbox_list *_list, const char *const *patterns,
+		  enum mailbox_list_iter_flags flags)
+{
+	struct fs_list_iterate_context *ctx;
+	pool_t pool;
+
+	if ((flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0) {
+		/* we're listing only subscribed mailboxes. we can't optimize
+		   it, so just use the generic code. */
+		return mailbox_list_subscriptions_iter_init(_list, patterns,
+							    flags);
+	}
+
+	pool = pool_alloconly_create("mailbox list fs iter", 2048);
+	ctx = p_new(pool, struct fs_list_iterate_context, 1);
+	ctx->ctx.pool = pool;
+	ctx->ctx.list = _list;
+	ctx->ctx.flags = flags;
+	array_create(&ctx->ctx.module_contexts, pool, sizeof(void *), 5);
+
+	ctx->info_pool = pool_alloconly_create("fs list", 1024);
+	ctx->sep = mail_namespace_get_sep(_list->ns);
+	ctx->info.ns = _list->ns;
+
+	if (!fs_list_get_valid_patterns(ctx, patterns)) {
+		/* we've only invalid patterns (or INBOX). create a glob
+		   anyway to avoid any crashes due to glob being accessed
+		   elsewhere */
+		ctx->ctx.glob = imap_match_init(pool, "", TRUE, ctx->sep);
+		return &ctx->ctx;
+	}
+	ctx->ctx.glob = imap_match_init_multiple(pool, ctx->valid_patterns,
+						 TRUE, ctx->sep);
+	fs_list_get_roots(ctx);
+	fs_list_next_root(ctx);
+	return &ctx->ctx;
+}
+
+int fs_list_iter_deinit(struct mailbox_list_iterate_context *_ctx)
+{
+	struct fs_list_iterate_context *ctx =
+		(struct fs_list_iterate_context *)_ctx;
+	int ret = _ctx->failed ? -1 : 0;
+
+	if ((_ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+		return mailbox_list_subscriptions_iter_deinit(_ctx);
+
+	while (ctx->dir != NULL) {
+		struct list_dir_context *dir = ctx->dir;
+
+		ctx->dir = dir->parent;
+		pool_unref(&dir->pool);
+	}
+
+	pool_unref(&ctx->info_pool);
+	pool_unref(&_ctx->pool);
+	return ret;
+}
+
+static void inbox_flags_set(struct fs_list_iterate_context *ctx)
+{
+	/* INBOX is always selectable */
+	ctx->info.flags &= ENUM_NEGATE(MAILBOX_NOSELECT | MAILBOX_NONEXISTENT);
+
+	if (mail_namespace_is_inbox_noinferiors(ctx->info.ns)) {
+		ctx->info.flags &= ENUM_NEGATE(MAILBOX_CHILDREN | MAILBOX_NOCHILDREN);
+		ctx->info.flags |= MAILBOX_NOINFERIORS;
+	}
+}
+
+static const char *
+fs_list_get_inbox_vname(struct fs_list_iterate_context *ctx)
+{
+	struct mail_namespace *ns = ctx->ctx.list->ns;
+
+	if ((ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0)
+		return "INBOX";
+	else
+		return p_strconcat(ctx->info_pool, ns->prefix, "INBOX", NULL);
+}
+
+static bool
+list_file_unfound_inbox(struct fs_list_iterate_context *ctx)
+{
+	ctx->info.flags = 0;
+	ctx->info.vname = fs_list_get_inbox_vname(ctx);
+
+	if (mailbox_list_mailbox(ctx->ctx.list, "INBOX", &ctx->info.flags) < 0)
+		ctx->ctx.failed = TRUE;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_NO_AUTO_BOXES) != 0 &&
+	    (ctx->info.flags & MAILBOX_NONEXISTENT) != 0)
+		return FALSE;
+
+	inbox_flags_set(ctx);
+	if (ctx->inbox_has_children)
+		ctx->info.flags |= MAILBOX_CHILDREN;
+	else {
+		/* we got here because we didn't see INBOX among other mailboxes,
+		   which means it has no children. */
+		ctx->info.flags |= MAILBOX_NOCHILDREN;
+	}
+	return TRUE;
+}
+
+static bool
+list_file_is_any_inbox(struct fs_list_iterate_context *ctx,
+		       const char *storage_name)
+{
+	const char *path, *inbox_path;
+
+	if (!fs_list_get_storage_path(ctx, storage_name, &path))
+		return FALSE;
+
+	if (mailbox_list_get_path(ctx->ctx.list, "INBOX",
+				  MAILBOX_LIST_PATH_TYPE_DIR, &inbox_path) <= 0)
+		i_unreached();
+	return strcmp(path, inbox_path) == 0;
+}
+
+static int
+fs_list_entry(struct fs_list_iterate_context *ctx,
+	      const struct list_dir_entry *entry)
+{
+	struct mail_namespace *ns = ctx->ctx.list->ns;
+	struct list_dir_context *dir, *subdir = NULL;
+	enum imap_match_result match, child_dir_match;
+	const char *storage_name, *vname, *child_dir_name;
+
+	dir = ctx->dir;
+	storage_name = dir_get_storage_name(dir, entry->fname);
+
+	vname = mailbox_list_get_vname(ctx->ctx.list, storage_name);
+	ctx->info.vname = p_strdup(ctx->info_pool, vname);
+	ctx->info.flags = entry->info_flags;
+
+	match = imap_match(ctx->ctx.glob, ctx->info.vname);
+
+	if (strcmp(ctx->info.vname, "INBOX") == 0 &&
+	    ctx->ctx.list->ns->prefix_len > 0) {
+		/* INBOX's children are matched as prefix/INBOX */
+		child_dir_name = t_strdup_printf("%sINBOX", ns->prefix);
+	} else {
+		child_dir_name =
+			t_strdup_printf("%s%c", ctx->info.vname, ctx->sep);
+	}
+	child_dir_match = imap_match(ctx->ctx.glob, child_dir_name);
+	if (child_dir_match == IMAP_MATCH_YES)
+		child_dir_match |= IMAP_MATCH_CHILDREN;
+
+	if ((ctx->info.flags &
+	     (MAILBOX_NOCHILDREN | MAILBOX_NOINFERIORS)) != 0) {
+		/* mailbox has no children */
+	} else if ((ctx->info.flags & MAILBOX_CHILDREN) != 0 &&
+		   (child_dir_match & IMAP_MATCH_CHILDREN) == 0) {
+		/* mailbox has children, but we don't want to list them */
+	} else if (((ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_CHILDREN) != 0 ||
+		    (child_dir_match & IMAP_MATCH_CHILDREN) != 0) &&
+		   *entry->fname != '\0') {
+		/* a) mailbox has children and we want to return them
+		   b) we don't want to return mailbox's children, but we need
+		   to know if it has any */
+		subdir = fs_list_read_dir(ctx, storage_name, entry->info_flags);
+		subdir->parent = dir;
+		ctx->dir = subdir;
+		/* the scanning may have updated the dir's info flags */
+		ctx->info.flags = subdir->info_flags;
+	}
+
+	/* handle INBOXes correctly */
+	if (strcasecmp(ctx->info.vname, "INBOX") == 0 &&
+	    (ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0) {
+		/* either this is user's INBOX, or it's a naming conflict */
+		if (!list_file_is_any_inbox(ctx, storage_name)) {
+			if (subdir == NULL) {
+				/* no children */
+			} else if ((ctx->ctx.list->flags &
+				    MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0) {
+				if (strcmp(storage_name, "INBOX") == 0) {
+					/* INBOX and its children are in
+					   different paths */
+					ctx->inbox_has_children = TRUE;
+				} else {
+					/* naming conflict, skip its
+					   children also */
+					ctx->dir = dir;
+					pool_unref(&subdir->pool);
+				}
+			} else if ((ctx->info.flags & MAILBOX_NOINFERIORS) == 0) {
+				/* INBOX itself is \NoInferiors, but this INBOX
+				   is a directory, and we can make INBOX have
+				   children using it. */
+				ctx->inbox_has_children = TRUE;
+			}
+			return 0;
+		}
+		if (subdir != NULL)
+			ctx->inbox_has_children = TRUE;
+		inbox_flags_set(ctx);
+		ctx->info.vname = "INBOX"; /* always return uppercased */
+		ctx->inbox_found = TRUE;
+	} else if (strcmp(storage_name, "INBOX") == 0 &&
+		   (ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0) {
+		/* this is <ns prefix>/INBOX. don't return it, unless it has
+		   children. */
+		i_assert(*ns->prefix != '\0');
+		if ((ctx->info.flags & MAILBOX_CHILDREN) == 0)
+			return 0;
+		/* although it could be selected with this name,
+		   it would be confusing for clients to see the same
+		   mails in both INBOX and <ns prefix>/INBOX. */
+		ctx->info.flags &= ENUM_NEGATE(MAILBOX_SELECT);
+		ctx->info.flags |= MAILBOX_NOSELECT;
+	} else if ((ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0 &&
+		   list_file_is_any_inbox(ctx, storage_name)) {
+		if ((ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0) {
+			/* probably mbox inbox file */
+			return 0;
+		}
+		/* shared/user/INBOX */
+		ctx->info.flags &= ENUM_NEGATE(MAILBOX_NOSELECT | MAILBOX_NONEXISTENT);
+		ctx->info.flags |= MAILBOX_SELECT;
+		ctx->inbox_found = TRUE;
+	}
+
+	if (match != IMAP_MATCH_YES) {
+		/* mailbox's children may match, but the mailbox itself
+		   doesn't */
+		return 0;
+	}
+	if (mailbox_list_iter_try_delete_noselect(&ctx->ctx, &ctx->info, storage_name))
+		return 0;
+	return 1;
+}
+
+static int
+fs_list_next(struct fs_list_iterate_context *ctx)
+{
+	struct list_dir_context *dir;
+	const struct list_dir_entry *entries;
+	unsigned int count;
+	int ret;
+
+	while (ctx->dir != NULL) {
+		/* NOTE: fs_list_entry() may change ctx->dir */
+		entries = array_get(&ctx->dir->entries, &count);
+		while (ctx->dir->entry_idx < count) {
+			p_clear(ctx->info_pool);
+			ret = fs_list_entry(ctx, &entries[ctx->dir->entry_idx++]);
+			if (ret > 0)
+				return 1;
+			if (ret < 0)
+				ctx->ctx.failed = TRUE;
+			entries = array_get(&ctx->dir->entries, &count);
+		}
+
+		dir = ctx->dir;
+		ctx->dir = dir->parent;
+		pool_unref(&dir->pool);
+
+		if (ctx->dir == NULL)
+			fs_list_next_root(ctx);
+	}
+
+	if (ctx->inbox_has_children && ctx->ctx.list->ns->prefix_len > 0 &&
+	    !ctx->listed_prefix_inbox) {
+		ctx->info.flags = MAILBOX_CHILDREN | MAILBOX_NOSELECT;
+		ctx->info.vname =
+			p_strconcat(ctx->info_pool,
+				    ctx->ctx.list->ns->prefix, "INBOX", NULL);
+		ctx->listed_prefix_inbox = TRUE;
+		if (imap_match(ctx->ctx.glob, ctx->info.vname) == IMAP_MATCH_YES)
+			return 1;
+	}
+	if (!ctx->inbox_found && ctx->ctx.glob != NULL &&
+	    (ctx->ctx.list->ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0 &&
+	    imap_match(ctx->ctx.glob,
+		       fs_list_get_inbox_vname(ctx)) == IMAP_MATCH_YES) {
+		/* INBOX wasn't seen while listing other mailboxes. It might
+		   be located elsewhere. */
+		ctx->inbox_found = TRUE;
+		return list_file_unfound_inbox(ctx) ? 1 : 0;
+	}
+
+	/* finished */
+	return 0;
+}
+
+const struct mailbox_info *
+fs_list_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	struct fs_list_iterate_context *ctx =
+		(struct fs_list_iterate_context *)_ctx;
+	int ret;
+
+	if ((_ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+		return mailbox_list_subscriptions_iter_next(_ctx);
+
+	T_BEGIN {
+		ret = fs_list_next(ctx);
+	} T_END;
+
+	if (ret == 0)
+		return mailbox_list_iter_default_next(_ctx);
+	else if (ret < 0)
+		return NULL;
+
+	if (_ctx->list->ns->type == MAIL_NAMESPACE_TYPE_SHARED &&
+	    !_ctx->list->ns->list->mail_set->mail_shared_explicit_inbox &&
+	    strlen(ctx->info.vname) < _ctx->list->ns->prefix_len) {
+		/* shared/user INBOX, IMAP code already lists it */
+		return fs_list_iter_next(_ctx);
+	}
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_SUBSCRIBED) != 0) {
+		mailbox_list_set_subscription_flags(ctx->ctx.list,
+						    ctx->info.vname,
+						    &ctx->info.flags);
+	}
+	i_assert(ctx->info.vname != NULL);
+	return &ctx->info;
+}
diff --git a/src/lib-storage/list/mailbox-list-fs.c b/src/lib-storage/list/mailbox-list-fs.c
new file mode 100644
index 0000000..c1aabb9
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-fs.c
@@ -0,0 +1,558 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hostpid.h"
+#include "mkdir-parents.h"
+#include "mailbox-log.h"
+#include "subscription-file.h"
+#include "mail-storage.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-delete.h"
+#include "mailbox-list-fs.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#define GLOBAL_TEMP_PREFIX ".temp."
+
+extern struct mailbox_list fs_mailbox_list;
+
+static struct mailbox_list *fs_list_alloc(void)
+{
+	struct fs_mailbox_list *list;
+	pool_t pool;
+
+	pool = pool_alloconly_create("fs list", 2048);
+
+	list = p_new(pool, struct fs_mailbox_list, 1);
+	list->list = fs_mailbox_list;
+	list->list.pool = pool;
+
+	list->temp_prefix = p_strconcat(pool, GLOBAL_TEMP_PREFIX,
+					my_hostname, ".", my_pid, ".", NULL);
+	return &list->list;
+}
+
+static void fs_list_deinit(struct mailbox_list *_list)
+{
+	struct fs_mailbox_list *list = (struct fs_mailbox_list *)_list;
+
+	pool_unref(&list->list.pool);
+}
+
+static char fs_list_get_hierarchy_sep(struct mailbox_list *list ATTR_UNUSED)
+{
+	return '/';
+}
+
+static const char *
+fs_list_get_path_to(const struct mailbox_list_settings *set,
+		    const char *root_dir, const char *name)
+{
+	if (*set->maildir_name != '\0' && set->index_control_use_maildir_name) {
+		return t_strdup_printf("%s/%s%s/%s", root_dir,
+				       set->mailbox_dir_name, name,
+				       set->maildir_name);
+	} else {
+		return t_strdup_printf("%s/%s%s", root_dir,
+				       set->mailbox_dir_name, name);
+	}
+}
+
+static int
+fs_list_get_path(struct mailbox_list *_list, const char *name,
+		 enum mailbox_list_path_type type, const char **path_r)
+{
+	const struct mailbox_list_settings *set = &_list->set;
+	const char *root_dir, *error;
+
+	if (name == NULL) {
+		/* return root directories */
+		return mailbox_list_set_get_root_path(set, type, path_r) ? 1 : 0;
+	}
+
+	i_assert(mailbox_list_is_valid_name(_list, name, &error));
+
+	if (mailbox_list_try_get_absolute_path(_list, &name)) {
+		if (type == MAILBOX_LIST_PATH_TYPE_INDEX &&
+		    *set->index_dir == '\0')
+			return 0;
+		*path_r = name;
+		return 1;
+	}
+
+	root_dir = set->root_dir;
+	switch (type) {
+	case MAILBOX_LIST_PATH_TYPE_DIR:
+		if (*set->maildir_name != '\0') {
+			*path_r = t_strdup_printf("%s/%s%s", set->root_dir,
+						  set->mailbox_dir_name, name);
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_PATH_TYPE_ALT_DIR:
+		if (set->alt_dir == NULL)
+			return 0;
+		if (*set->maildir_name != '\0') {
+			/* maildir_name is for the mailbox, caller is asking
+			   for the directory name */
+			*path_r = t_strdup_printf("%s/%s%s", set->alt_dir,
+						  set->mailbox_dir_name, name);
+			return 1;
+		}
+		root_dir = set->alt_dir;
+		break;
+	case MAILBOX_LIST_PATH_TYPE_MAILBOX:
+		break;
+	case MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX:
+		if (set->alt_dir == NULL)
+			return 0;
+		root_dir = set->alt_dir;
+		break;
+	case MAILBOX_LIST_PATH_TYPE_CONTROL:
+		if (set->control_dir != NULL) {
+			*path_r = fs_list_get_path_to(set, set->control_dir, name);
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_PATH_TYPE_INDEX_CACHE:
+		if (set->index_cache_dir != NULL) {
+			*path_r = fs_list_get_path_to(set, set->index_cache_dir, name);
+			return 1;
+		}
+		/* fall through */
+	case MAILBOX_LIST_PATH_TYPE_INDEX:
+		if (set->index_dir != NULL) {
+			if (*set->index_dir == '\0')
+				return 0;
+			*path_r = fs_list_get_path_to(set, set->index_dir, name);
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_PATH_TYPE_INDEX_PRIVATE:
+		if (set->index_pvt_dir == NULL)
+			return 0;
+		*path_r = fs_list_get_path_to(set, set->index_pvt_dir, name);
+		return 1;
+	case MAILBOX_LIST_PATH_TYPE_LIST_INDEX:
+		i_unreached();
+	}
+
+	if (type == MAILBOX_LIST_PATH_TYPE_ALT_DIR ||
+	    type == MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX) {
+		/* don't use inbox_path */
+	} else if (strcmp(name, "INBOX") == 0 && set->inbox_path != NULL) {
+		/* If INBOX is a file, index and control directories are
+		   located in root directory. */
+		if ((_list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0 ||
+		    type == MAILBOX_LIST_PATH_TYPE_MAILBOX ||
+		    type == MAILBOX_LIST_PATH_TYPE_DIR) {
+			*path_r = set->inbox_path;
+			return 1;
+		}
+	}
+
+	if (root_dir == NULL)
+		return 0;
+	if (*set->maildir_name == '\0') {
+		*path_r = t_strdup_printf("%s/%s%s", root_dir,
+					  set->mailbox_dir_name, name);
+	} else {
+		*path_r = t_strdup_printf("%s/%s%s/%s", root_dir,
+					  set->mailbox_dir_name, name,
+					  set->maildir_name);
+	}
+	return 1;
+}
+
+static const char *
+fs_list_get_temp_prefix(struct mailbox_list *_list, bool global)
+{
+	struct fs_mailbox_list *list = (struct fs_mailbox_list *)_list;
+
+	return global ? GLOBAL_TEMP_PREFIX : list->temp_prefix;
+}
+
+static const char *
+fs_list_join_refpattern(struct mailbox_list *_list ATTR_UNUSED,
+			const char *ref, const char *pattern)
+{
+	if (*pattern == '/' || *pattern == '~') {
+		/* pattern overrides reference */
+	} else if (*ref != '\0') {
+		/* merge reference and pattern */
+		pattern = t_strconcat(ref, pattern, NULL);
+	}
+	return pattern;
+}
+
+static int fs_list_set_subscribed(struct mailbox_list *_list,
+				  const char *name, bool set)
+{
+	struct fs_mailbox_list *list = (struct fs_mailbox_list *)_list;
+	enum mailbox_list_path_type type;
+	const char *path;
+
+	if (_list->set.subscription_fname == NULL) {
+		mailbox_list_set_error(_list, MAIL_ERROR_NOTPOSSIBLE,
+				       "Subscriptions not supported");
+		return -1;
+	}
+
+	type = _list->set.control_dir != NULL ?
+		MAILBOX_LIST_PATH_TYPE_CONTROL : MAILBOX_LIST_PATH_TYPE_DIR;
+
+	path = t_strconcat(mailbox_list_get_root_forced(_list, type),
+			   "/", _list->set.subscription_fname, NULL);
+	return subsfile_set_subscribed(_list, path, list->temp_prefix,
+				       name, set);
+}
+
+
+static const char *mailbox_list_fs_get_trash_dir(struct mailbox_list *list)
+{
+	const char *root_dir;
+
+	root_dir = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_DIR);
+	return t_strdup_printf("%s/"MAILBOX_LIST_FS_TRASH_DIR_NAME, root_dir);
+}
+
+static int
+fs_list_delete_maildir(struct mailbox_list *list, const char *name)
+{
+	const char *path, *trash_dir;
+	bool rmdir_path;
+	int ret;
+
+	if (*list->set.maildir_name != '\0' &&
+	    *list->set.mailbox_dir_name != '\0') {
+		trash_dir = mailbox_list_fs_get_trash_dir(list);
+		ret = mailbox_list_delete_maildir_via_trash(list, name,
+							    trash_dir);
+		if (ret < 0)
+			return -1;
+
+		if (ret > 0) {
+			/* try to delete the parent directory */
+			if (mailbox_list_get_path(list, name,
+						  MAILBOX_LIST_PATH_TYPE_DIR,
+						  &path) <= 0)
+				i_unreached();
+			if (rmdir(path) < 0 && errno != ENOENT &&
+			    errno != ENOTEMPTY && errno != EEXIST) {
+				mailbox_list_set_critical(list,
+					"rmdir(%s) failed: %m", path);
+			}
+			return 0;
+		}
+	}
+
+	rmdir_path = *list->set.maildir_name != '\0';
+	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &path) <= 0)
+		i_unreached();
+	return mailbox_list_delete_mailbox_nonrecursive(list, name, path,
+							rmdir_path);
+}
+
+static int fs_list_delete_mailbox(struct mailbox_list *list, const char *name)
+{
+	const char *path;
+	int ret;
+
+	ret = mailbox_list_get_path(list, name,
+				    MAILBOX_LIST_PATH_TYPE_MAILBOX, &path);
+	if (ret < 0)
+		return -1;
+	i_assert(ret > 0);
+
+	if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+		ret = mailbox_list_delete_mailbox_file(list, name, path);
+	} else {
+		ret = fs_list_delete_maildir(list, name);
+	}
+	if (ret == 0 && list->set.no_noselect)
+		mailbox_list_delete_until_root(list, path, MAILBOX_LIST_PATH_TYPE_MAILBOX);
+
+	i_assert(ret <= 0);
+	return mailbox_list_delete_finish_ret(list, name, ret == 0);
+}
+
+static int fs_list_rmdir(struct mailbox_list *list, const char *name,
+			 const char *path)
+{
+	guid_128_t dir_sha128;
+
+	if (rmdir(path) < 0)
+		return -1;
+
+	mailbox_name_get_sha128(name, dir_sha128);
+	mailbox_list_add_change(list, MAILBOX_LOG_RECORD_DELETE_DIR,
+				dir_sha128);
+	return 0;
+}
+
+static int fs_list_delete_dir(struct mailbox_list *list, const char *name)
+{
+	const char *path, *child_name, *child_path, *p;
+	char sep;
+	int ret;
+
+	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_DIR,
+				  &path) <= 0)
+		i_unreached();
+	ret = fs_list_rmdir(list, name, path);
+	if (!list->set.iter_from_index_dir) {
+		/* it should exist only in the mail directory */
+		if (ret == 0)
+			return 0;
+	} else if (ret == 0 || errno == ENOENT) {
+		/* the primary list location is the index directory, but it
+		   exists in both index and mail directories. */
+		if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_INDEX,
+					  &path) <= 0)
+			i_unreached();
+		if (fs_list_rmdir(list, name, path) == 0)
+			return 0;
+		if (ret == 0 && errno == ENOENT) {
+			/* partial existence: exists in _DIR, but not in
+			   _INDEX. return success anyway. */
+			return 0;
+		}
+		/* a) both directories didn't exist
+		   b) index directory couldn't be rmdir()ed for some reason */
+	}
+
+	if (errno == ENOENT || errno == ENOTDIR) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+			T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+	} else if (errno == ENOTEMPTY || errno == EEXIST) {
+		/* mbox workaround: if only .imap/ directory is preventing the
+		   deletion, remove it */
+		sep = mailbox_list_get_hierarchy_sep(list);
+		child_name = t_strdup_printf("%s%cchild", name, sep);
+		if (mailbox_list_get_path(list, child_name,
+					  MAILBOX_LIST_PATH_TYPE_INDEX,
+					  &child_path) > 0 &&
+		    str_begins(child_path, path)) {
+			/* drop the "/child" part out. */
+			p = strrchr(child_path, '/');
+			if (rmdir(t_strdup_until(child_path, p)) == 0) {
+				/* try again */
+				if (fs_list_rmdir(list, name, path) == 0)
+					return 0;
+			}
+		}
+
+		mailbox_list_set_error(list, MAIL_ERROR_EXISTS,
+			"Mailbox has children, delete them first");
+	} else {
+		mailbox_list_set_critical(list, "rmdir(%s) failed: %m", path);
+	}
+	return -1;
+}
+
+static int rename_dir(struct mailbox_list *oldlist, const char *oldname,
+		      struct mailbox_list *newlist, const char *newname,
+		      enum mailbox_list_path_type type, bool rmdir_parent)
+{
+	struct stat st;
+	const char *oldpath, *newpath, *p, *oldparent, *newparent;
+
+	if (mailbox_list_get_path(oldlist, oldname, type, &oldpath) <= 0 ||
+	    mailbox_list_get_path(newlist, newname, type, &newpath) <= 0)
+		return 0;
+
+	if (strcmp(oldpath, newpath) == 0)
+		return 0;
+
+	p = strrchr(oldpath, '/');
+	oldparent = p == NULL ? "/" : t_strdup_until(oldpath, p);
+	p = strrchr(newpath, '/');
+	newparent = p == NULL ? "/" : t_strdup_until(newpath, p);
+
+	if (strcmp(oldparent, newparent) != 0 && stat(oldpath, &st) == 0) {
+		/* make sure the newparent exists */
+		struct mailbox_permissions perm;
+
+		mailbox_list_get_root_permissions(newlist, &perm);
+		if (mkdir_parents_chgrp(newparent, perm.dir_create_mode,
+					perm.file_create_gid,
+					perm.file_create_gid_origin) < 0 &&
+		    errno != EEXIST) {
+			if (mailbox_list_set_error_from_errno(oldlist))
+				return -1;
+
+			mailbox_list_set_critical(oldlist,
+				"mkdir_parents(%s) failed: %m", newparent);
+			return -1;
+		}
+	}
+
+	if (rename(oldpath, newpath) < 0 && errno != ENOENT) {
+		mailbox_list_set_critical(oldlist, "rename(%s, %s) failed: %m",
+					  oldpath, newpath);
+		return -1;
+	}
+	if (rmdir_parent && (p = strrchr(oldpath, '/')) != NULL) {
+		oldpath = t_strdup_until(oldpath, p);
+		if (rmdir(oldpath) < 0 && errno != ENOENT &&
+		    errno != ENOTEMPTY && errno != EEXIST) {
+			mailbox_list_set_critical(oldlist,
+				"rmdir(%s) failed: %m", oldpath);
+		}
+	}
+
+	/* avoid leaving empty directories lying around */
+	mailbox_list_delete_until_root(oldlist, oldpath, type);
+	return 0;
+}
+
+static int fs_list_rename_mailbox(struct mailbox_list *oldlist,
+				  const char *oldname,
+				  struct mailbox_list *newlist,
+				  const char *newname)
+{
+	struct mail_storage *oldstorage;
+	const char *oldvname, *oldpath, *newpath, *alt_newpath, *root_path, *p;
+	struct stat st;
+	struct mailbox_permissions old_perm, new_perm;
+	bool rmdir_parent = FALSE;
+
+	oldvname = mailbox_list_get_vname(oldlist, oldname);
+	if (mailbox_list_get_storage(&oldlist, oldvname, &oldstorage) < 0)
+		return -1;
+
+	if (mailbox_list_get_path(oldlist, oldname,
+				  MAILBOX_LIST_PATH_TYPE_DIR, &oldpath) <= 0 ||
+	    mailbox_list_get_path(newlist, newname,
+				  MAILBOX_LIST_PATH_TYPE_DIR, &newpath) <= 0)
+		i_unreached();
+	if (mailbox_list_get_path(newlist, newname, MAILBOX_LIST_PATH_TYPE_ALT_DIR,
+				  &alt_newpath) < 0)
+		i_unreached();
+
+	root_path = mailbox_list_get_root_forced(oldlist, MAILBOX_LIST_PATH_TYPE_MAILBOX);
+	if (strcmp(oldpath, root_path) == 0) {
+		/* most likely INBOX */
+		mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			t_strdup_printf("Renaming %s isn't supported.",
+					oldname));
+		return -1;
+	}
+
+	mailbox_list_get_permissions(oldlist, oldname, &old_perm);
+	mailbox_list_get_permissions(newlist, newname, &new_perm);
+
+	/* if we're renaming under another mailbox, require its permissions
+	   to be same as ours. */
+	if (strchr(newname, mailbox_list_get_hierarchy_sep(newlist)) != NULL &&
+	    (new_perm.file_create_mode != old_perm.file_create_mode ||
+	     new_perm.dir_create_mode != old_perm.dir_create_mode ||
+	     new_perm.file_create_gid != old_perm.file_create_gid)) {
+		mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			"Renaming not supported across conflicting "
+			"directory permissions");
+		return -1;
+	}
+
+	/* create the hierarchy */
+	p = strrchr(newpath, '/');
+	if (p != NULL) {
+		p = t_strdup_until(newpath, p);
+		if (mkdir_parents_chgrp(p, new_perm.dir_create_mode,
+					new_perm.file_create_gid,
+					new_perm.file_create_gid_origin) < 0 &&
+		    errno != EEXIST) {
+			if (mailbox_list_set_error_from_errno(oldlist))
+				return -1;
+
+			mailbox_list_set_critical(oldlist,
+				"mkdir_parents(%s) failed: %m", p);
+			return -1;
+		}
+	}
+
+	/* first check that the destination mailbox doesn't exist.
+	   this is racy, but we need to be atomic and there's hardly any
+	   possibility that someone actually tries to rename two mailboxes
+	   to same new one */
+	if (lstat(newpath, &st) == 0) {
+		mailbox_list_set_error(oldlist, MAIL_ERROR_EXISTS,
+				       "Target mailbox already exists");
+		return -1;
+	} else if (errno == ENOTDIR) {
+		mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			"Target mailbox doesn't allow inferior mailboxes");
+		return -1;
+	} else if (errno != ENOENT && errno != EACCES) {
+		mailbox_list_set_critical(oldlist, "lstat(%s) failed: %m",
+					  newpath);
+		return -1;
+	}
+
+	if (alt_newpath != NULL) {
+		if (stat(alt_newpath, &st) == 0) {
+			/* race condition or a directory left there lying around?
+			   safest to just report error. */
+			mailbox_list_set_error(oldlist, MAIL_ERROR_EXISTS,
+					       "Target mailbox already exists");
+			return -1;
+		} else if (errno != ENOENT) {
+			mailbox_list_set_critical(oldlist, "stat(%s) failed: %m",
+						  alt_newpath);
+			return -1;
+		}
+	}
+
+	if (rename(oldpath, newpath) < 0) {
+		if (ENOTFOUND(errno)) {
+			mailbox_list_set_error(oldlist, MAIL_ERROR_NOTFOUND,
+				T_MAILBOX_LIST_ERR_NOT_FOUND(oldlist, oldname));
+		} else if (!mailbox_list_set_error_from_errno(oldlist)) {
+			mailbox_list_set_critical(oldlist,
+				"rename(%s, %s) failed: %m", oldpath, newpath);
+		}
+		return -1;
+	}
+
+	if (alt_newpath != NULL) {
+		(void)rename_dir(oldlist, oldname, newlist, newname,
+				 MAILBOX_LIST_PATH_TYPE_ALT_DIR, rmdir_parent);
+	}
+	(void)rename_dir(oldlist, oldname, newlist, newname,
+			 MAILBOX_LIST_PATH_TYPE_CONTROL, rmdir_parent);
+	(void)rename_dir(oldlist, oldname, newlist, newname,
+			 MAILBOX_LIST_PATH_TYPE_INDEX, rmdir_parent);
+	(void)rename_dir(oldlist, oldname, newlist, newname,
+			 MAILBOX_LIST_PATH_TYPE_INDEX_CACHE, rmdir_parent);
+	return 0;
+}
+
+struct mailbox_list fs_mailbox_list = {
+	.name = MAILBOX_LIST_NAME_FS,
+	.props = 0,
+	.mailbox_name_max_length = MAILBOX_LIST_NAME_MAX_LENGTH,
+
+	.v = {
+		.alloc = fs_list_alloc,
+		.deinit = fs_list_deinit,
+		.get_hierarchy_sep = fs_list_get_hierarchy_sep,
+		.get_vname = mailbox_list_default_get_vname,
+		.get_storage_name = mailbox_list_default_get_storage_name,
+		.get_path = fs_list_get_path,
+		.get_temp_prefix = fs_list_get_temp_prefix,
+		.join_refpattern = fs_list_join_refpattern,
+		.iter_init = fs_list_iter_init,
+		.iter_next = fs_list_iter_next,
+		.iter_deinit = fs_list_iter_deinit,
+		.get_mailbox_flags = fs_list_get_mailbox_flags,
+		.subscriptions_refresh = mailbox_list_subscriptions_refresh,
+		.set_subscribed = fs_list_set_subscribed,
+		.delete_mailbox = fs_list_delete_mailbox,
+		.delete_dir = fs_list_delete_dir,
+		.delete_symlink = mailbox_list_delete_symlink_default,
+		.rename_mailbox = fs_list_rename_mailbox,
+	}
+};
diff --git a/src/lib-storage/list/mailbox-list-fs.h b/src/lib-storage/list/mailbox-list-fs.h
new file mode 100644
index 0000000..3841890
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-fs.h
@@ -0,0 +1,28 @@
+#ifndef MAILBOX_LIST_FS_H
+#define MAILBOX_LIST_FS_H
+
+#include "mailbox-list-private.h"
+
+/* When doing deletion via renaming it first to trash directory, use this as
+   the trash directory name */
+#define MAILBOX_LIST_FS_TRASH_DIR_NAME "..DOVECOT-TrasH"
+
+struct fs_mailbox_list {
+	struct mailbox_list list;
+
+	const char *temp_prefix;
+};
+
+struct mailbox_list_iterate_context *
+fs_list_iter_init(struct mailbox_list *_list, const char *const *patterns,
+		  enum mailbox_list_iter_flags flags);
+int fs_list_iter_deinit(struct mailbox_list_iterate_context *ctx);
+const struct mailbox_info *
+fs_list_iter_next(struct mailbox_list_iterate_context *ctx);
+
+int fs_list_get_mailbox_flags(struct mailbox_list *list,
+			      const char *dir, const char *fname,
+			      enum mailbox_list_file_type type,
+			      enum mailbox_info_flags *flags);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-index-backend.c b/src/lib-storage/list/mailbox-list-index-backend.c
new file mode 100644
index 0000000..e088f3b
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-backend.c
@@ -0,0 +1,970 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hostpid.h"
+#include "str.h"
+#include "mail-index.h"
+#include "subscription-file.h"
+#include "mailbox-list-delete.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-index-storage.h"
+#include "mailbox-list-index-sync.h"
+
+#include <stdio.h>
+
+#define GLOBAL_TEMP_PREFIX ".temp."
+#define MAILBOX_LIST_INDEX_DEFAULT_ESCAPE_CHAR '^'
+
+struct index_mailbox_list {
+	struct mailbox_list list;
+	const char *temp_prefix;
+
+	const char *create_mailbox_name;
+	guid_128_t create_mailbox_guid;
+};
+
+extern struct mailbox_list index_mailbox_list;
+
+static int
+index_list_rename_mailbox(struct mailbox_list *_oldlist, const char *oldname,
+			  struct mailbox_list *_newlist, const char *newname);
+
+static struct mailbox_list *index_list_alloc(void)
+{
+	struct index_mailbox_list *list;
+	pool_t pool;
+
+	pool = pool_alloconly_create("index list", 2048);
+
+	list = p_new(pool, struct index_mailbox_list, 1);
+	list->list = index_mailbox_list;
+	list->list.pool = pool;
+	list->list.set.storage_name_escape_char = MAILBOX_LIST_INDEX_DEFAULT_ESCAPE_CHAR;
+
+	list->temp_prefix = p_strconcat(pool, GLOBAL_TEMP_PREFIX,
+					my_hostname, ".", my_pid, ".", NULL);
+	return &list->list;
+}
+
+static int index_list_init(struct mailbox_list *_list, const char **error_r)
+{
+	if (!_list->mail_set->mailbox_list_index) {
+		*error_r = "LAYOUT=index requires mailbox_list_index=yes";
+		return -1;
+	}
+	return 0;
+}
+
+static void index_list_deinit(struct mailbox_list *_list)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+
+	pool_unref(&list->list.pool);
+}
+
+static char index_list_get_hierarchy_sep(struct mailbox_list *list)
+{
+	char sep = list->ns->set->separator[0];
+
+	if (sep == '\0')
+		sep = MAILBOX_LIST_INDEX_HIERARCHY_SEP;
+	if (sep == list->set.storage_name_escape_char) {
+		/* Separator conflicts with the escape character.
+		   Use something else. */
+		if (sep != MAILBOX_LIST_INDEX_HIERARCHY_SEP)
+			sep = MAILBOX_LIST_INDEX_HIERARCHY_SEP;
+		else
+			sep = MAILBOX_LIST_INDEX_HIERARCHY_ALT_SEP;
+	}
+	return sep;
+}
+
+static int
+index_list_get_refreshed_node_seq(struct index_mailbox_list *list,
+				  struct mail_index_view *view,
+				  const char *name,
+				  struct mailbox_list_index_node **node_r,
+				  uint32_t *seq_r)
+{
+	unsigned int i;
+
+	*node_r = NULL;
+	*seq_r = 0;
+
+	for (i = 0; i < 2; i++) {
+		*node_r = mailbox_list_index_lookup(&list->list, name);
+		if (*node_r == NULL)
+			return 0;
+		if (mail_index_lookup_seq(view, (*node_r)->uid, seq_r))
+			return 1;
+		/* mailbox was just expunged. refreshing should notice it. */
+		if (mailbox_list_index_refresh_force(&list->list) < 0)
+			return -1;
+	}
+	i_panic("mailbox list index: refreshing doesn't lose expunged uid=%u",
+		(*node_r)->uid);
+	return -1;
+}
+
+static const char *
+index_get_guid_path(struct mailbox_list *_list, const char *root_dir,
+		    const guid_128_t mailbox_guid)
+{
+	return t_strdup_printf("%s/%s%s", root_dir,
+			       _list->set.mailbox_dir_name,
+			       guid_128_to_string(mailbox_guid));
+}
+
+static int
+index_list_get_path(struct mailbox_list *_list, const char *name,
+		    enum mailbox_list_path_type type, const char **path_r)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+	struct mail_index_view *view;
+	struct mailbox_list_index_node *node;
+	struct mailbox_status status;
+	guid_128_t mailbox_guid;
+	const char *root_dir, *reason;
+	uint32_t seq;
+	int ret;
+
+	if (name == NULL) {
+		/* return root directories */
+		return mailbox_list_set_get_root_path(&_list->set, type,
+						      path_r) ? 1 : 0;
+	}
+	/* consistently use mailbox_dir_name as part of all mailbox
+	   directories (index/control/etc) */
+	switch (type) {
+	case MAILBOX_LIST_PATH_TYPE_MAILBOX:
+		type = MAILBOX_LIST_PATH_TYPE_DIR;
+		break;
+	case MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX:
+		type = MAILBOX_LIST_PATH_TYPE_ALT_DIR;
+		break;
+	case MAILBOX_LIST_PATH_TYPE_LIST_INDEX:
+		i_unreached();
+	default:
+		break;
+	}
+	if (!mailbox_list_set_get_root_path(&_list->set, type, &root_dir))
+		return 0;
+
+	if (list->create_mailbox_name != NULL &&
+	    strcmp(list->create_mailbox_name, name) == 0) {
+		*path_r = index_get_guid_path(_list, root_dir,
+					      list->create_mailbox_guid);
+		return 1;
+	}
+
+	/* ilist is only required from this point onwards.
+	   At least imapc calls index_list_get_path without this context*/
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(_list);
+
+	if (ilist->sync_ctx != NULL) {
+		/* we could get here during sync from
+		   index_list_mailbox_create_selectable() */
+		view = ilist->sync_ctx->view;
+		node = mailbox_list_index_lookup(&list->list, name);
+		if (node == NULL) {
+			seq = 0;
+			ret = 0;
+		} else if (mail_index_lookup_seq(view, node->uid, &seq)) {
+			ret = 1;
+		} else {
+			i_panic("mailbox list index: lost uid=%u", node->uid);
+		}
+	} else {
+		if (mailbox_list_index_refresh(&list->list) < 0)
+			return -1;
+		view = mail_index_view_open(ilist->index);
+		ret = index_list_get_refreshed_node_seq(list, view, name, &node, &seq);
+		if (ret < 0) {
+			mail_index_view_close(&view);
+			return -1;
+		}
+	}
+	i_assert(ret == 0 || seq != 0);
+	if (ret == 0) {
+		mailbox_list_set_error(_list, MAIL_ERROR_NOTFOUND,
+				       T_MAIL_ERR_MAILBOX_NOT_FOUND(name));
+		ret = -1;
+	} else if (!mailbox_list_index_status(_list, view, seq, 0,
+					      &status, mailbox_guid,
+					      NULL, &reason) ||
+		   guid_128_is_empty(mailbox_guid)) {
+		mailbox_list_set_error(_list, MAIL_ERROR_NOTFOUND,
+				       T_MAIL_ERR_MAILBOX_NOT_FOUND(name));
+		ret = -1;
+	} else {
+		*path_r = index_get_guid_path(_list, root_dir, mailbox_guid);
+		ret = 1;
+	}
+	if (ilist->sync_ctx == NULL)
+		mail_index_view_close(&view);
+	return ret;
+}
+
+static const char *
+index_list_get_temp_prefix(struct mailbox_list *_list, bool global)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+
+	return global ? GLOBAL_TEMP_PREFIX : list->temp_prefix;
+}
+
+static int index_list_set_subscribed(struct mailbox_list *_list,
+				     const char *name, bool set)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+	const char *path;
+
+	if (_list->set.subscription_fname == NULL) {
+		mailbox_list_set_error(_list, MAIL_ERROR_NOTPOSSIBLE,
+				       "Subscriptions not supported");
+		return -1;
+	}
+
+	path = t_strconcat(_list->set.control_dir != NULL ?
+			   _list->set.control_dir : _list->set.root_dir,
+			   "/", _list->set.subscription_fname, NULL);
+	return subsfile_set_subscribed(_list, path, list->temp_prefix,
+				       name, set);
+}
+
+static int
+index_list_node_exists(struct index_mailbox_list *list, const char *name,
+		       enum mailbox_existence *existence_r)
+{
+	struct mailbox_list_index_node *node;
+
+	*existence_r = MAILBOX_EXISTENCE_NONE;
+
+	if (mailbox_list_index_refresh(&list->list) < 0)
+		return -1;
+
+	node = mailbox_list_index_lookup(&list->list, name);
+	if (node == NULL)
+		return 0;
+
+	if ((node->flags & (MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+			    MAILBOX_LIST_INDEX_FLAG_NOSELECT)) == 0) {
+		/* selectable */
+		*existence_r = MAILBOX_EXISTENCE_SELECT;
+	} else {
+		/* non-selectable */
+		*existence_r = MAILBOX_EXISTENCE_NOSELECT;
+	}
+	return 0;
+}
+
+static int
+index_list_mailbox_create_dir(struct index_mailbox_list *list, const char *name)
+{
+	struct mailbox_list_index_sync_context *sync_ctx;
+	struct mailbox_list_index_node *node;
+	uint32_t seq;
+	bool created;
+	int ret;
+
+	if (mailbox_list_index_sync_begin(&list->list, &sync_ctx) < 0)
+		return -1;
+
+	seq = mailbox_list_index_sync_name(sync_ctx, name, &node, &created);
+	if (created || (node->flags & MAILBOX_LIST_INDEX_FLAG_NONEXISTENT) != 0) {
+		/* didn't already exist */
+		node->flags = MAILBOX_LIST_INDEX_FLAG_NOSELECT;
+		mail_index_update_flags(sync_ctx->trans, seq, MODIFY_REPLACE,
+					(enum mail_flags)node->flags);
+		ret = 1;
+	} else {
+		/* already existed */
+		ret = 0;
+	}
+	if (mailbox_list_index_sync_end(&sync_ctx, TRUE) < 0)
+		ret = -1;
+	return ret;
+}
+
+static int
+index_list_mailbox_create_selectable(struct mailbox *box,
+				     const guid_128_t mailbox_guid)
+{
+	struct index_mailbox_list *list =
+		(struct index_mailbox_list *)box->list;
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mailbox_list_index_sync_context *sync_ctx;
+	struct mailbox_list_index_record rec;
+	struct mailbox_list_index_node *node;
+	const void *data;
+	bool expunged, created;
+	uint32_t seq;
+
+	if (mailbox_list_index_sync_begin(&list->list, &sync_ctx) < 0)
+		return -1;
+
+	seq = mailbox_list_index_sync_name(sync_ctx, box->name, &node, &created);
+	if (box->corrupted_mailbox_name) {
+		/* an existing mailbox is being created with a "unknown" name.
+		   opening the mailbox will hopefully find its real name and
+		   rename it. */
+		node->flags |= MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME;
+		mail_index_update_flags(sync_ctx->trans, seq, MODIFY_ADD,
+			(enum mail_flags)MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME);
+	}
+	if (!created &&
+	    (node->flags & (MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+			    MAILBOX_LIST_INDEX_FLAG_NOSELECT)) == 0) {
+		/* already selectable */
+		(void)mailbox_list_index_sync_end(&sync_ctx, TRUE);
+		return 0;
+	}
+
+	mail_index_lookup_ext(sync_ctx->view, seq, ilist->ext_id,
+			      &data, &expunged);
+	i_assert(data != NULL && !expunged);
+	memcpy(&rec, data, sizeof(rec));
+	i_assert(guid_128_is_empty(rec.guid));
+
+	/* make it selectable */
+	node->flags &= ENUM_NEGATE(MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+				   MAILBOX_LIST_INDEX_FLAG_NOSELECT |
+				   MAILBOX_LIST_INDEX_FLAG_NOINFERIORS);
+	mail_index_update_flags(sync_ctx->trans, seq, MODIFY_REPLACE,
+				(enum mail_flags)node->flags);
+
+	/* set UIDVALIDITY if was set by the storage */
+	if (box->index != NULL) {
+		struct mail_index_view *view;
+
+		view = mail_index_view_open(box->index);
+		if (mail_index_get_header(view)->uid_validity != 0)
+			rec.uid_validity = mail_index_get_header(view)->uid_validity;
+		mail_index_view_close(&view);
+	}
+
+	/* set GUID */
+	memcpy(rec.guid, mailbox_guid, sizeof(rec.guid));
+	mail_index_update_ext(sync_ctx->trans, seq, ilist->ext_id, &rec, NULL);
+
+	if (mailbox_list_index_sync_end(&sync_ctx, TRUE) < 0) {
+		/* make sure we forget any changes done internally */
+		mailbox_list_index_reset(ilist);
+		return -1;
+	}
+	return 1;
+}
+
+static int
+index_list_mailbox_create(struct mailbox *box,
+			  const struct mailbox_update *update, bool directory)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	struct index_mailbox_list *list =
+		(struct index_mailbox_list *)box->list;
+	struct mailbox_update new_update;
+	enum mailbox_existence existence;
+	int ret;
+
+	/* first do a quick check that it doesn't exist */
+	if (index_list_node_exists(list, box->name, &existence) < 0) {
+		mail_storage_copy_list_error(box->storage, box->list);
+		return -1;
+	}
+	if (existence == MAILBOX_EXISTENCE_NONE && directory) {
+		/* now add the directory to index locked */
+		if ((ret = index_list_mailbox_create_dir(list, box->name)) < 0) {
+			mail_storage_copy_list_error(box->storage, box->list);
+			return -1;
+		}
+	} else if (existence != MAILBOX_EXISTENCE_SELECT && !directory) {
+		/* if no GUID is requested, generate it ourself. set
+		   UIDVALIDITY to index sometimes later. */
+		if (update == NULL)
+			i_zero(&new_update);
+		else
+			new_update = *update;
+		if (guid_128_is_empty(new_update.mailbox_guid))
+			guid_128_generate(new_update.mailbox_guid);
+
+		/* create the backend mailbox first before it exists in the
+		   list. the mailbox creation wants to use get_path() though,
+		   so use a bit kludgy create_mailbox_* variables during the
+		   creation to return the path. we'll also support recursively
+		   creating more mailboxes in here. */
+		const char *old_name;
+		guid_128_t old_guid;
+
+		old_name = list->create_mailbox_name;
+		guid_128_copy(old_guid, list->create_mailbox_guid);
+
+		list->create_mailbox_name = box->name;
+		guid_128_copy(list->create_mailbox_guid, new_update.mailbox_guid);
+
+		ret = ibox->module_ctx.super.create_box(box, &new_update, FALSE);
+
+		if (ret == 0) {
+			/* backend mailbox was successfully created. now add it
+			   to the list. */
+			ret = index_list_mailbox_create_selectable(box, new_update.mailbox_guid);
+			if (ret < 0)
+				mail_storage_copy_list_error(box->storage, box->list);
+			if (ret <= 0) {
+				/* failed to add to list. rollback the backend
+				   mailbox creation */
+				bool create_error = ret < 0;
+
+				if (create_error)
+					mail_storage_last_error_push(box->storage);
+				if (mailbox_delete(box) < 0)
+					ret = -1;
+				if (create_error)
+					mail_storage_last_error_pop(box->storage);
+			}
+		}
+		list->create_mailbox_name = old_name;
+		guid_128_copy(list->create_mailbox_guid, old_guid);
+		if (ret < 0)
+			return ret;
+	} else {
+		ret = 0;
+	}
+
+	if (ret == 0) {
+		mail_storage_set_error(box->storage, MAIL_ERROR_EXISTS,
+				       "Mailbox already exists");
+		return -1;
+	}
+	return 0;
+}
+
+static int
+index_list_mailbox_update(struct mailbox *box,
+			  const struct mailbox_update *update)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	const char *root_dir, *old_path, *new_path;
+
+	if (mailbox_list_get_path(box->list, box->name,
+				  MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &old_path) <= 0)
+		old_path = NULL;
+
+	if (ibox->module_ctx.super.update_box(box, update) < 0)
+		return -1;
+
+	/* rename the directory */
+	if (!guid_128_is_empty(update->mailbox_guid) && old_path != NULL &&
+	    mailbox_list_set_get_root_path(&box->list->set,
+					   MAILBOX_LIST_PATH_TYPE_DIR,
+					   &root_dir)) {
+		new_path = index_get_guid_path(box->list, root_dir,
+					       update->mailbox_guid);
+		if (strcmp(old_path, new_path) == 0)
+			;
+		else if (rename(old_path, new_path) == 0)
+			;
+		else if (errno == ENOENT) {
+			mail_storage_set_error(box->storage, MAIL_ERROR_NOTFOUND,
+				T_MAIL_ERR_MAILBOX_NOT_FOUND(box->name));
+			return -1;
+		} else {
+			mailbox_set_critical(box, "rename(%s, %s) failed: %m",
+					     old_path, new_path);
+			return -1;
+		}
+	}
+
+	mailbox_list_index_update_mailbox_index(box, update);
+	return 0;
+}
+
+static int
+index_list_mailbox_exists(struct mailbox *box, bool auto_boxes,
+			  enum mailbox_existence *existence_r)
+{
+	if (auto_boxes && mailbox_is_autocreated(box)) {
+		*existence_r = MAILBOX_EXISTENCE_SELECT;
+		return 0;
+	}
+
+	struct index_mailbox_list *list =
+		(struct index_mailbox_list *)box->list;
+
+	if (index_list_node_exists(list, box->name, existence_r) < 0) {
+		mail_storage_copy_list_error(box->storage, box->list);
+		return -1;
+	}
+	return 0;
+}
+
+static bool mailbox_has_corrupted_name(struct mailbox *box)
+{
+	struct mailbox_list_index_node *node;
+
+	if (box->corrupted_mailbox_name)
+		return TRUE;
+
+	node = mailbox_list_index_lookup(box->list, box->name);
+	return node != NULL &&
+		(node->flags & MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME) != 0;
+}
+
+static void index_list_rename_corrupted(struct mailbox *box, const char *newname)
+{
+	if (index_list_rename_mailbox(box->list, box->name,
+				      box->list, newname) == 0 ||
+	    box->list->error != MAIL_ERROR_EXISTS)
+		return;
+
+	/* mailbox already exists. don't give up yet, just use the newname
+	   as prefix and add the "lost-xx" as suffix. */
+	char sep = mailbox_list_get_hierarchy_sep(box->list);
+	const char *oldname = box->name;
+
+	/* oldname should be at the root level, but check for hierarchies
+	   anyway to be safe. */
+	const char *p = strrchr(oldname, sep);
+	if (p != NULL)
+		oldname = p+1;
+
+	newname = t_strdup_printf("%s-%s", newname, oldname);
+	(void)index_list_rename_mailbox(box->list, box->name,
+					box->list, newname);
+}
+
+static int index_list_mailbox_open(struct mailbox *box)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	const void *data;
+	const unsigned char *name_hdr;
+	size_t name_hdr_size;
+
+	if (ibox->module_ctx.super.open(box) < 0)
+		return -1;
+
+	if (box->view == NULL) {
+		/* FIXME: dsync-merge is performing a delete in obox - remove
+		   this check once dsync-merging is no longer used. */
+		return 0;
+	}
+
+	/* if mailbox name has changed, update it to the header. Use \0
+	   as the hierarchy separator in the header. This is to make sure
+	   we don't keep rewriting the name just in case some backend switches
+	   between separators when accessed different ways. */
+
+	/* Get the current mailbox name with \0 separators and unesacped. */
+	size_t box_name_len;
+	const unsigned char *box_zerosep_name =
+		mailbox_name_hdr_encode(box->list, box->name, &box_name_len);
+
+	/* Does it match what's in the header now? */
+	mail_index_get_header_ext(box->view, box->box_name_hdr_ext_id,
+				  &data, &name_hdr_size);
+	name_hdr = data;
+	while (name_hdr_size > 0 && name_hdr[name_hdr_size-1] == '\0') {
+		/* Remove trailing \0 - header doesn't shrink always */
+		name_hdr_size--;
+	}
+	if (name_hdr_size == box_name_len &&
+	    memcmp(box_zerosep_name, name_hdr, box_name_len) == 0) {
+		/* Same mailbox name */
+	} else if (!mailbox_has_corrupted_name(box)) {
+		/* Mailbox name changed - update */
+		struct mail_index_transaction *trans =
+			mail_index_transaction_begin(box->view, 0);
+		mail_index_ext_resize_hdr(trans, box->box_name_hdr_ext_id,
+					  box_name_len);
+		mail_index_update_header_ext(trans, box->box_name_hdr_ext_id, 0,
+					     box_zerosep_name, box_name_len);
+		(void)mail_index_transaction_commit(&trans);
+	} else if (name_hdr_size > 0) {
+		/* Mailbox name is corrupted. Rename it to the previous name. */
+		const char *newname =
+			mailbox_name_hdr_decode_storage_name(
+				box->list, name_hdr, name_hdr_size);
+		index_list_rename_corrupted(box, newname);
+	}
+	return 0;
+}
+
+void mailbox_list_index_backend_sync_init(struct mailbox *box,
+					  enum mailbox_sync_flags flags)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+
+	if ((flags & MAILBOX_SYNC_FLAG_FORCE_RESYNC) != 0 &&
+	    !ilist->force_resynced) {
+		enum mail_storage_list_index_rebuild_reason reason =
+			MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_FORCE_RESYNC;
+
+		if (box->storage->v.list_index_rebuild != NULL &&
+		    box->storage->v.list_index_rebuild(box->storage, reason) < 0)
+			ilist->force_resync_failed = TRUE;
+		/* try to rebuild list index only once - even if it failed */
+		ilist->force_resynced = TRUE;
+	}
+}
+
+int mailbox_list_index_backend_sync_deinit(struct mailbox *box)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+
+	if (ilist->force_resync_failed) {
+		/* fail this only once */
+		ilist->force_resync_failed = FALSE;
+		return -1;
+	}
+	return 0;
+}
+
+static void
+index_list_try_delete(struct mailbox_list *_list, const char *name,
+		      enum mailbox_list_path_type type)
+{
+	const char *mailbox_path, *path, *error;
+
+	if (mailbox_list_get_path(_list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				  &mailbox_path) <= 0 ||
+	    mailbox_list_get_path(_list, name, type, &path) <= 0 ||
+	    strcmp(path, mailbox_path) == 0)
+		return;
+
+	if (*_list->set.maildir_name == '\0' &&
+	    (_list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0) {
+		/* this directory may contain also child mailboxes' data.
+		   we don't want to delete that. */
+		bool rmdir_path = *_list->set.maildir_name != '\0';
+		if (mailbox_list_delete_mailbox_nonrecursive(_list, name, path,
+							     rmdir_path) < 0)
+			return;
+	} else {
+		if (mailbox_list_delete_trash(path, &error) < 0 &&
+		    errno != ENOTEMPTY) {
+			mailbox_list_set_critical(_list,
+				"unlink_directory(%s) failed: %s", path, error);
+		}
+	}
+
+	/* avoid leaving empty directories lying around */
+	mailbox_list_delete_until_root(_list, path, type);
+}
+
+static void
+index_list_delete_finish(struct mailbox_list *list, const char *name)
+{
+	index_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_INDEX);
+	index_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_CONTROL);
+	index_list_try_delete(list, name, MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX);
+}
+
+static int
+index_list_delete_entry(struct index_mailbox_list *list, const char *name,
+			bool delete_selectable)
+{
+	struct mailbox_list_index_sync_context *sync_ctx;
+	int ret;
+
+	if (list->create_mailbox_name != NULL &&
+	    strcmp(name, list->create_mailbox_name) == 0) {
+		/* we're rolling back a failed create. if the name exists in the
+		   list, it was done by somebody else so we don't want to
+		   remove it. */
+		return 0;
+	}
+
+	if (mailbox_list_index_sync_begin(&list->list, &sync_ctx) < 0)
+		return -1;
+	ret = mailbox_list_index_sync_delete(sync_ctx, name, delete_selectable);
+	if (mailbox_list_index_sync_end(&sync_ctx, TRUE) < 0)
+		return -1;
+	return ret;
+}
+
+static int
+index_list_try_delete_nonexistent_parent(struct mailbox_list *_list,
+					 const char *name)
+{
+	struct index_mailbox_list *list =
+		container_of(_list, struct index_mailbox_list, list);
+	struct mailbox_list_index_node *node;
+	string_t *full_name;
+	const char *p;
+	char sep = mailbox_list_get_hierarchy_sep(_list);
+
+	if ((p = strrchr(name, sep)) == NULL) {
+		/* No occurrences of the hierarchy separator could be found
+		   in the name, so the mailbox has no parents. */
+               return 0;
+	}
+
+	/* Lookup parent node of of given "name" */
+	node = mailbox_list_index_lookup(_list, t_strdup_until(name, p));
+	full_name = t_str_new(32);
+
+	while (node != NULL) {
+		/* Attempt to delete all parent nodes that are NOSELECT or
+		   NONEXISTENT */
+		if (node->children != NULL)
+			break;
+		if ((node->flags & MAILBOX_LIST_INDEX_FLAG_NOSELECT) != 0 ||
+		    (node->flags & MAILBOX_LIST_INDEX_FLAG_NONEXISTENT) != 0) {
+			/* The parent mailbox has no other children and is not
+			   existant or not selectable, delete it */
+			str_truncate(full_name, 0);
+			mailbox_list_index_node_get_path(node, sep, full_name);
+			if (index_list_delete_entry(list, str_c(full_name), FALSE) < 0)
+				return -1;
+
+			if ((p = strrchr(str_c(full_name), sep)) == NULL) {
+				/* No occurrences of the hierarchy separator
+				   could be found in the mailbox that was
+				   just deleted. */
+				node = NULL;
+			} else {
+				/* lookup parent node of the node just deleted */
+				str_truncate(full_name, p - str_c(full_name));
+				node = mailbox_list_index_lookup(_list, str_c(full_name));
+			}
+		} else
+			break;
+
+	}
+	return 0;
+}
+
+static int
+index_list_delete_mailbox(struct mailbox_list *_list, const char *name)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+	const char *path;
+	int ret;
+
+	/* first delete the mailbox files */
+	ret = mailbox_list_get_path(_list, name, MAILBOX_LIST_PATH_TYPE_MAILBOX,
+				    &path);
+	if (ret <= 0)
+		return ret;
+
+	if ((_list->flags & (MAILBOX_LIST_FLAG_NO_MAIL_FILES |
+			     MAILBOX_LIST_FLAG_NO_DELETES)) != 0) {
+		ret = 0;
+	} else if ((_list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+		ret = mailbox_list_delete_mailbox_file(_list, name, path);
+	} else {
+		ret = mailbox_list_delete_mailbox_nonrecursive(_list, name,
+							       path, TRUE);
+	}
+
+	if ((ret == 0 || (_list->props & MAILBOX_LIST_PROP_AUTOCREATE_DIRS) != 0) &&
+	    (_list->flags & MAILBOX_LIST_FLAG_NO_DELETES) == 0)
+		index_list_delete_finish(_list, name);
+	if (ret == 0) {
+		if (index_list_delete_entry(list, name, TRUE) < 0)
+			return -1;
+	}
+	if (_list->set.no_noselect && ret == 0)
+		(void)index_list_try_delete_nonexistent_parent(_list, name);
+
+	return ret;
+}
+
+static int
+index_list_delete_dir(struct mailbox_list *_list, const char *name)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_list;
+	int ret;
+
+	if ((ret = index_list_delete_entry(list, name, FALSE)) < 0)
+		return -1;
+	if (ret == 0) {
+		mailbox_list_set_error(_list, MAIL_ERROR_EXISTS,
+			"Mailbox has children, delete them first");
+		return -1;
+	}
+	return 0;
+}
+
+static int
+index_list_delete_symlink(struct mailbox_list *_list,
+			  const char *name ATTR_UNUSED)
+{
+	mailbox_list_set_error(_list, MAIL_ERROR_NOTPOSSIBLE,
+			       "Symlinks not supported");
+	return -1;
+}
+
+static int
+index_list_rename_mailbox(struct mailbox_list *_oldlist, const char *oldname,
+			  struct mailbox_list *_newlist, const char *newname)
+{
+	struct index_mailbox_list *list = (struct index_mailbox_list *)_oldlist;
+	const size_t oldname_len = strlen(oldname);
+	struct mailbox_list_index_sync_context *sync_ctx;
+	struct mailbox_list_index_record oldrec, newrec;
+	struct mailbox_list_index_node *oldnode, *newnode, *child;
+	const void *data;
+	bool created, expunged;
+	uint32_t oldseq, newseq;
+	int ret;
+
+	if (_oldlist != _newlist) {
+		mailbox_list_set_error(_oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			"Renaming not supported across namespaces.");
+		return -1;
+	}
+
+	if (str_begins(newname, oldname) &&
+	   newname[oldname_len] == mailbox_list_get_hierarchy_sep(_newlist)) {
+		mailbox_list_set_error(_oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			"Can't rename mailbox under itself.");
+		return -1;
+	}
+
+	if (mailbox_list_index_sync_begin(&list->list, &sync_ctx) < 0)
+		return -1;
+
+	oldnode = mailbox_list_index_lookup(&list->list, oldname);
+	if (oldnode == NULL) {
+		(void)mailbox_list_index_sync_end(&sync_ctx, FALSE);
+		mailbox_list_set_error(&list->list, MAIL_ERROR_NOTFOUND,
+			T_MAIL_ERR_MAILBOX_NOT_FOUND(oldname));
+		return -1;
+	}
+	if (!mail_index_lookup_seq(sync_ctx->view, oldnode->uid, &oldseq))
+		i_panic("mailbox list index: lost uid=%u", oldnode->uid);
+
+	newseq = mailbox_list_index_sync_name(sync_ctx, newname,
+					      &newnode, &created);
+	if (!created) {
+		(void)mailbox_list_index_sync_end(&sync_ctx, FALSE);
+		mailbox_list_set_error(&list->list, MAIL_ERROR_EXISTS,
+				       "Target mailbox already exists");
+		return -1;
+	}
+	i_assert(oldnode != newnode);
+
+	/* copy all the data from old node to new node */
+	newnode->uid = oldnode->uid;
+	newnode->flags = oldnode->flags;
+	newnode->children = oldnode->children; oldnode->children = NULL;
+	for (child = newnode->children; child != NULL; child = child->next)
+		child->parent = newnode;
+
+	/* remove the old node from existence */
+	mailbox_list_index_node_unlink(sync_ctx->ilist, oldnode);
+
+	/* update the old index record to contain the new name_id/parent_uid,
+	   then expunge the added index record */
+	mail_index_lookup_ext(sync_ctx->view, oldseq, sync_ctx->ilist->ext_id,
+			      &data, &expunged);
+	i_assert(data != NULL && !expunged);
+	memcpy(&oldrec, data, sizeof(oldrec));
+
+	mail_index_lookup_ext(sync_ctx->view, newseq, sync_ctx->ilist->ext_id,
+			      &data, &expunged);
+	i_assert(data != NULL && !expunged);
+	memcpy(&newrec, data, sizeof(newrec));
+
+	oldrec.name_id = newrec.name_id;
+	oldrec.parent_uid = newrec.parent_uid;
+
+	if ((newnode->flags & MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME) != 0) {
+		/* mailbox is renamed - clear away the corruption flag so the
+		   new name will be written to the mailbox index header. */
+		newnode->flags &= ENUM_NEGATE(MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME);
+		mail_index_update_flags(sync_ctx->trans, oldseq, MODIFY_REMOVE,
+			(enum mail_flags)MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME);
+	}
+	mail_index_update_ext(sync_ctx->trans, oldseq,
+			      sync_ctx->ilist->ext_id, &oldrec, NULL);
+	mail_index_expunge(sync_ctx->trans, newseq);
+
+	ret = mailbox_list_index_sync_end(&sync_ctx, TRUE);
+
+	if (_oldlist->set.no_noselect && ret == 0)
+               (void)index_list_try_delete_nonexistent_parent(_oldlist, oldname);
+
+	return ret;
+}
+
+static struct mailbox_list_iterate_context *
+index_list_iter_init(struct mailbox_list *list,
+		     const char *const *patterns,
+		     enum mailbox_list_iter_flags flags)
+{
+	struct mailbox_list_iterate_context *ctx;
+	pool_t pool;
+
+	if ((flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0) {
+		return mailbox_list_subscriptions_iter_init(list, patterns,
+							    flags);
+	}
+
+	pool = pool_alloconly_create("mailbox list index backend iter", 1024);
+	ctx = p_new(pool, struct mailbox_list_iterate_context, 1);
+	ctx->pool = pool;
+	ctx->list = list;
+	ctx->flags = flags;
+	array_create(&ctx->module_contexts, pool, sizeof(void *), 5);
+	return ctx;
+}
+
+static const struct mailbox_info *
+index_list_iter_next(struct mailbox_list_iterate_context *ctx)
+{
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+		return mailbox_list_subscriptions_iter_next(ctx);
+	return NULL;
+}
+
+static int index_list_iter_deinit(struct mailbox_list_iterate_context *ctx)
+{
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+		return mailbox_list_subscriptions_iter_deinit(ctx);
+	pool_unref(&ctx->pool);
+	return 0;
+}
+
+struct mailbox_list index_mailbox_list = {
+	.name = MAILBOX_LIST_NAME_INDEX,
+	.props = MAILBOX_LIST_PROP_NO_ROOT | MAILBOX_LIST_PROP_NO_INTERNAL_NAMES,
+	.mailbox_name_max_length = MAILBOX_LIST_NAME_MAX_LENGTH,
+
+	.v = {
+		.alloc = index_list_alloc,
+		.init = index_list_init,
+		.deinit = index_list_deinit,
+		.get_hierarchy_sep = index_list_get_hierarchy_sep,
+		.get_vname = mailbox_list_default_get_vname,
+		.get_storage_name = mailbox_list_default_get_storage_name,
+		.get_path = index_list_get_path,
+		.get_temp_prefix = index_list_get_temp_prefix,
+		.iter_init = index_list_iter_init,
+		.iter_next = index_list_iter_next,
+		.iter_deinit = index_list_iter_deinit,
+		.subscriptions_refresh = mailbox_list_subscriptions_refresh,
+		.set_subscribed = index_list_set_subscribed,
+		.delete_mailbox = index_list_delete_mailbox,
+		.delete_dir = index_list_delete_dir,
+		.delete_symlink = index_list_delete_symlink,
+		.rename_mailbox = index_list_rename_mailbox,
+	}
+};
+
+bool mailbox_list_index_backend_init_mailbox(struct mailbox *box,
+					     struct mailbox_vfuncs *v)
+{
+	if (strcmp(box->list->name, MAILBOX_LIST_NAME_INDEX) != 0)
+		return TRUE;
+
+	/* NOTE: this is using the same v as
+	   mailbox_list_index_status_init_mailbox(), so don't have them
+	   accidentally override each others. */
+	v->create_box = index_list_mailbox_create;
+	v->update_box = index_list_mailbox_update;
+	v->exists = index_list_mailbox_exists;
+	v->open = index_list_mailbox_open;
+	return FALSE;
+}
diff --git a/src/lib-storage/list/mailbox-list-index-iter.c b/src/lib-storage/list/mailbox-list-index-iter.c
new file mode 100644
index 0000000..680808e
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-iter.c
@@ -0,0 +1,266 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "imap-match.h"
+#include "mail-storage.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-iter-private.h"
+#include "mailbox-list-index.h"
+
+static bool iter_use_index(struct mailbox_list *list,
+			   enum mailbox_list_iter_flags flags)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	if ((flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0) {
+		/* for now we don't use indexes when listing subscriptions,
+		   because it needs to list also the nonexistent subscribed
+		   mailboxes, which don't exist in the index. */
+		return FALSE;
+	}
+	if ((flags & MAILBOX_LIST_ITER_RAW_LIST) != 0 &&
+	    ilist->has_backing_store) {
+		/* no indexing wanted with raw lists */
+		return FALSE;
+	}
+	if (mailbox_list_index_refresh(list) < 0 &&
+	    ilist->has_backing_store) {
+		/* refresh failed */
+		return FALSE;
+	}
+	return TRUE;
+}
+
+struct mailbox_list_iterate_context *
+mailbox_list_index_iter_init(struct mailbox_list *list,
+			     const char *const *patterns,
+			     enum mailbox_list_iter_flags flags)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_iterate_context *ctx;
+	pool_t pool;
+	char ns_sep = mail_namespace_get_sep(list->ns);
+
+	if (!iter_use_index(list, flags)) {
+		/* no indexing */
+		return ilist->module_ctx.super.iter_init(list, patterns, flags);
+	}
+
+	pool = pool_alloconly_create("mailbox list index iter", 2048);
+	ctx = p_new(pool, struct mailbox_list_index_iterate_context, 1);
+	ctx->ctx.pool = pool;
+	ctx->ctx.list = list;
+	ctx->ctx.flags = flags;
+	ctx->ctx.glob = imap_match_init_multiple(pool, patterns, TRUE, ns_sep);
+	array_create(&ctx->ctx.module_contexts, pool, sizeof(void *), 5);
+	ctx->info_pool = pool_alloconly_create("mailbox list index iter info", 128);
+	ctx->ctx.index_iteration = TRUE;
+
+	/* listing mailboxes from index */
+	ctx->info.ns = list->ns;
+	ctx->path = str_new(pool, 128);
+	ctx->next_node = ilist->mailbox_tree;
+	ctx->mailbox_pool = ilist->mailbox_pool;
+	pool_ref(ctx->mailbox_pool);
+	return &ctx->ctx;
+}
+
+static void
+mailbox_list_get_escaped_mailbox_name(struct mailbox_list *list,
+				      const char *raw_name,
+				      string_t *escaped_name)
+{
+	const char escape_chars[] = {
+		list->set.storage_name_escape_char,
+		mailbox_list_get_hierarchy_sep(list),
+		'\0'
+	};
+	mailbox_list_name_escape(raw_name, escape_chars, escaped_name);
+}
+
+static void
+mailbox_list_index_update_info(struct mailbox_list_index_iterate_context *ctx)
+{
+	struct mailbox_list_index_node *node = ctx->next_node;
+	struct mailbox *box;
+
+	p_clear(ctx->info_pool);
+
+	str_truncate(ctx->path, ctx->parent_len);
+	/* the root directory may have an empty name. in that case we'll still
+	   want to insert the separator, so check for non-NULL parent rather
+	   than non-empty path. */
+	if (node->parent != NULL) {
+		str_append_c(ctx->path,
+			     mailbox_list_get_hierarchy_sep(ctx->ctx.list));
+	}
+	mailbox_list_get_escaped_mailbox_name(ctx->ctx.list, node->raw_name,
+					      ctx->path);
+
+	ctx->info.vname = mailbox_list_get_vname(ctx->ctx.list, str_c(ctx->path));
+	ctx->info.flags = node->children != NULL ?
+		MAILBOX_CHILDREN : MAILBOX_NOCHILDREN;
+	if (strcmp(ctx->info.vname, "INBOX") != 0) {
+		/* non-INBOX */
+		ctx->info.vname = p_strdup(ctx->info_pool, ctx->info.vname);
+	} else if (!ctx->prefix_inbox_list) {
+		/* listing INBOX itself */
+		ctx->info.vname = "INBOX";
+		if (mail_namespace_is_inbox_noinferiors(ctx->info.ns)) {
+			ctx->info.flags &= ENUM_NEGATE(MAILBOX_CHILDREN |
+						       MAILBOX_NOCHILDREN);
+			ctx->info.flags |= MAILBOX_NOINFERIORS;
+		}
+	} else {
+		/* listing INBOX/INBOX */
+		ctx->info.vname = p_strconcat(ctx->info_pool,
+			ctx->ctx.list->ns->prefix, "INBOX", NULL);
+		ctx->info.flags |= MAILBOX_NONEXISTENT;
+	}
+	if ((node->flags & MAILBOX_LIST_INDEX_FLAG_NONEXISTENT) != 0)
+		ctx->info.flags |= MAILBOX_NONEXISTENT;
+	else if ((node->flags & MAILBOX_LIST_INDEX_FLAG_NOSELECT) != 0)
+		ctx->info.flags |= MAILBOX_NOSELECT;
+	if ((node->flags & MAILBOX_LIST_INDEX_FLAG_NOINFERIORS) != 0)
+		ctx->info.flags |= MAILBOX_NOINFERIORS;
+
+	if ((ctx->ctx.flags & (MAILBOX_LIST_ITER_SELECT_SUBSCRIBED |
+			       MAILBOX_LIST_ITER_RETURN_SUBSCRIBED)) != 0) {
+		mailbox_list_set_subscription_flags(ctx->ctx.list,
+						    ctx->info.vname,
+						    &ctx->info.flags);
+	}
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_NO_FLAGS) == 0) {
+		box = mailbox_alloc(ctx->ctx.list, ctx->info.vname, 0);
+		mailbox_list_index_status_set_info_flags(box, node->uid,
+							 &ctx->info.flags);
+		mailbox_free(&box);
+	}
+}
+
+static void
+mailbox_list_index_update_next(struct mailbox_list_index_iterate_context *ctx,
+			       bool follow_children)
+{
+	struct mailbox_list_index_node *node = ctx->next_node;
+
+	if (!ctx->prefix_inbox_list && ctx->ctx.list->ns->prefix_len > 0 &&
+	    strcmp(node->raw_name, "INBOX") == 0 && node->parent == NULL &&
+	    node->children != NULL) {
+		/* prefix/INBOX has children */
+		ctx->prefix_inbox_list = TRUE;
+		return;
+	}
+
+	if (node->children != NULL && follow_children) {
+		ctx->parent_len = str_len(ctx->path);
+		ctx->next_node = node->children;
+	} else {
+		while (node->next == NULL) {
+			node = node->parent;
+			if (node != NULL) T_BEGIN {
+				/* The storage name kept in the iteration context
+				   is escaped. To calculate the right truncation
+				   margin, the length of the name must be
+				   calculated from the escaped storage name and
+				   not from node->raw_name. */
+				string_t *escaped_name = t_str_new(64);
+				mailbox_list_get_escaped_mailbox_name(ctx->ctx.list,
+								      node->raw_name,
+								      escaped_name);
+				ctx->parent_len -= str_len(escaped_name);
+				if (node->parent != NULL)
+					ctx->parent_len--;
+			} T_END;
+			if (node == NULL) {
+				/* last one */
+				ctx->next_node = NULL;
+				return;
+			}
+		}
+		ctx->next_node = node->next;
+	}
+}
+
+static bool
+iter_subscriptions_ok(struct mailbox_list_index_iterate_context *ctx)
+{
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0)
+		return TRUE;
+
+	if ((ctx->info.flags & MAILBOX_SUBSCRIBED) != 0)
+		return TRUE;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SELECT_RECURSIVEMATCH) != 0 &&
+	    (ctx->info.flags & MAILBOX_CHILD_SUBSCRIBED) != 0)
+		return TRUE;
+	return FALSE;
+}
+
+const struct mailbox_info *
+mailbox_list_index_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(_ctx->list);
+	if (!_ctx->index_iteration) {
+		/* index isn't being used */
+		return ilist->module_ctx.super.iter_next(_ctx);
+	}
+
+	struct mailbox_list_index_iterate_context *ctx =
+		(struct mailbox_list_index_iterate_context *)_ctx;
+	bool follow_children;
+	enum imap_match_result match;
+
+	/* listing mailboxes from index */
+	while (ctx->next_node != NULL) {
+		T_BEGIN {
+			mailbox_list_index_update_info(ctx);
+		} T_END;
+		match = imap_match(_ctx->glob, ctx->info.vname);
+
+		follow_children = (match & (IMAP_MATCH_YES |
+					    IMAP_MATCH_CHILDREN)) != 0;
+		if (match == IMAP_MATCH_YES && iter_subscriptions_ok(ctx)) {
+			/* If this is a) \NoSelect leaf, b) not LAYOUT=index
+			   and c) NO-NOSELECT is set, try to rmdir the leaf
+			   directores from filesystem. (With LAYOUT=index the
+			   \NoSelect mailboxes aren't on the filesystem.) */
+			if (ilist->has_backing_store &&
+			    mailbox_list_iter_try_delete_noselect(_ctx, &ctx->info,
+								  str_c(ctx->path))) {
+				/* Deleted \NoSelect leaf. Refresh the index
+				   later on so it gets removed from the index
+				   as well. */
+				mailbox_list_index_refresh_later(_ctx->list);
+			} else {
+				mailbox_list_index_update_next(ctx, TRUE);
+				return &ctx->info;
+			}
+		} else if ((_ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0 &&
+			   (ctx->info.flags & MAILBOX_CHILD_SUBSCRIBED) == 0) {
+			/* listing only subscriptions, but there are no
+			   subscribed children. */
+			follow_children = FALSE;
+		}
+		mailbox_list_index_update_next(ctx, follow_children);
+	}
+	return mailbox_list_iter_default_next(_ctx);
+}
+
+int mailbox_list_index_iter_deinit(struct mailbox_list_iterate_context *_ctx)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(_ctx->list);
+	if (!_ctx->index_iteration)
+		return ilist->module_ctx.super.iter_deinit(_ctx);
+
+	struct mailbox_list_index_iterate_context *ctx =
+		(struct mailbox_list_index_iterate_context *)_ctx;
+	int ret = ctx->failed ? -1 : 0;
+
+	pool_unref(&ctx->mailbox_pool);
+	pool_unref(&ctx->info_pool);
+	pool_unref(&_ctx->pool);
+	return ret;
+}
diff --git a/src/lib-storage/list/mailbox-list-index-notify.c b/src/lib-storage/list/mailbox-list-index-notify.c
new file mode 100644
index 0000000..c07e95b
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-notify.c
@@ -0,0 +1,967 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "str.h"
+#include "mail-index-private.h"
+#include "mail-transaction-log-private.h"
+#include "mail-storage-private.h"
+#include "mailbox-list-notify.h"
+#include "mailbox-list-notify-tree.h"
+#include "mailbox-list-index.h"
+
+#include <sys/stat.h>
+
+#define NOTIFY_DELAY_MSECS 500
+
+enum ilist_ext_type {
+	ILIST_EXT_NONE,
+	ILIST_EXT_BASE,
+	ILIST_EXT_MSGS,
+	ILIST_EXT_HIGHESTMODSEQ,
+	ILIST_EXT_UNKNOWN
+};
+
+struct mailbox_list_notify_rename {
+	uint32_t old_uid, new_uid;
+};
+
+struct mailbox_list_inotify_entry {
+	uint32_t uid;
+	guid_128_t guid;
+	bool expunge;
+};
+
+struct mailbox_list_notify_index {
+	struct mailbox_list_notify notify;
+
+	struct mailbox_tree_context *subscriptions;
+	struct mailbox_list_notify_tree *tree;
+	struct mail_index_view *view, *old_view;
+	struct mail_index_view_sync_ctx *sync_ctx;
+	enum ilist_ext_type cur_ext;
+	uint32_t cur_ext_id;
+
+	void (*wait_callback)(void *context);
+	void *wait_context;
+	struct io *io_wait, *io_wait_inbox;
+	struct timeout *to_wait, *to_notify;
+
+	ARRAY_TYPE(seq_range) new_uids, expunged_uids, changed_uids;
+	ARRAY_TYPE(const_string) new_subscriptions, new_unsubscriptions;
+	ARRAY(struct mailbox_list_notify_rename) renames;
+	struct seq_range_iter new_uids_iter, expunged_uids_iter;
+	struct seq_range_iter changed_uids_iter;
+	unsigned int new_uids_n, expunged_uids_n, changed_uids_n;
+	unsigned int rename_idx, subscription_idx, unsubscription_idx;
+
+	struct mailbox_list_notify_rec notify_rec;
+	string_t *rec_name;
+
+	char *list_log_path, *inbox_log_path;
+	struct stat list_last_st, inbox_last_st;
+	struct mailbox *inbox;
+
+	bool initialized:1;
+	bool read_failed:1;
+	bool inbox_event_pending:1;
+};
+
+static const enum mailbox_status_items notify_status_items =
+	STATUS_UIDVALIDITY | STATUS_UIDNEXT | STATUS_MESSAGES |
+	STATUS_UNSEEN | STATUS_HIGHESTMODSEQ;
+
+static enum mailbox_list_notify_event
+mailbox_list_index_get_changed_events(const struct mailbox_notify_node *nnode,
+				      const struct mailbox_status *status)
+{
+	enum mailbox_list_notify_event events = 0;
+
+	if (nnode->uidvalidity != status->uidvalidity)
+		events |= MAILBOX_LIST_NOTIFY_UIDVALIDITY;
+	if (nnode->uidnext != status->uidnext)
+		events |= MAILBOX_LIST_NOTIFY_APPENDS;
+	if (nnode->messages > status->messages) {
+		/* NOTE: not entirely reliable, since there could be both
+		   expunges and appends.. but it shouldn't make any difference
+		   in practise, since anybody interested in expunges is most
+		   likely also interested in appends. */
+		events |= MAILBOX_LIST_NOTIFY_EXPUNGES;
+	}
+	if (nnode->unseen != status->unseen)
+		events |= MAILBOX_LIST_NOTIFY_SEEN_CHANGES;
+	if (nnode->highest_modseq < status->highest_modseq)
+		events |= MAILBOX_LIST_NOTIFY_MODSEQ_CHANGES;
+	return events;
+}
+
+static void
+mailbox_notify_node_update_status(struct mailbox_notify_node *nnode,
+				  struct mailbox_status *status)
+{
+	nnode->uidvalidity = status->uidvalidity;
+	nnode->uidnext = status->uidnext;
+	nnode->messages = status->messages;
+	nnode->unseen = status->unseen;
+	nnode->highest_modseq = status->highest_modseq;
+}
+
+static void
+mailbox_list_index_notify_init_inbox(struct mailbox_list_notify_index *inotify)
+{
+	inotify->inbox = mailbox_alloc(inotify->notify.list, "INBOX",
+				       MAILBOX_FLAG_READONLY);
+	if (mailbox_open(inotify->inbox) < 0)
+		mailbox_free(&inotify->inbox);
+	else
+		inotify->inbox_log_path =
+			i_strconcat(inotify->inbox->index->filepath,
+				    ".log", NULL);
+}
+
+int mailbox_list_index_notify_init(struct mailbox_list *list,
+				   enum mailbox_list_notify_event mask,
+				   struct mailbox_list_notify **notify_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(list);
+	struct mailbox_list_notify_index *inotify;
+	const char *index_dir;
+
+	if (ilist == NULL) {
+		/* can't do this without mailbox list indexes */
+		return -1;
+	}
+
+	(void)mailbox_list_index_refresh(list);
+
+	inotify = i_new(struct mailbox_list_notify_index, 1);
+	inotify->notify.list = list;
+	inotify->notify.mask = mask;
+	inotify->view = mail_index_view_open(ilist->index);
+	inotify->old_view = mail_index_view_dup_private(inotify->view);
+	inotify->tree = mailbox_list_notify_tree_init(list);
+	i_array_init(&inotify->new_uids, 8);
+	i_array_init(&inotify->expunged_uids, 8);
+	i_array_init(&inotify->changed_uids, 16);
+	i_array_init(&inotify->renames, 16);
+	i_array_init(&inotify->new_subscriptions, 16);
+	i_array_init(&inotify->new_unsubscriptions, 16);
+	inotify->rec_name = str_new(default_pool, 64);
+	if ((mask & (MAILBOX_LIST_NOTIFY_SUBSCRIBE |
+		     MAILBOX_LIST_NOTIFY_UNSUBSCRIBE)) != 0) {
+		(void)mailbox_list_iter_subscriptions_refresh(list);
+		mailbox_tree_sort(list->subscriptions);
+		inotify->subscriptions = mailbox_tree_dup(list->subscriptions);
+	}
+	inotify->list_log_path = i_strdup(ilist->index->log->filepath);
+	if (list->mail_set->mailbox_list_index_include_inbox) {
+		/* INBOX can be handled also using mailbox list index */
+	} else if ((list->ns->flags & NAMESPACE_FLAG_INBOX_ANY) == 0) {
+		/* no INBOX in this namespace */
+	} else if ((mask & MAILBOX_LIST_NOTIFY_STATUS) == 0) {
+		/* not interested in mailbox changes */
+	} else if (mailbox_list_get_path(list, "INBOX", MAILBOX_LIST_PATH_TYPE_INDEX,
+					 &index_dir) <= 0) {
+		/* no indexes for INBOX? can't handle it */
+	} else {
+		mailbox_list_index_notify_init_inbox(inotify);
+	}
+
+	*notify_r = &inotify->notify;
+	return 1;
+}
+
+void mailbox_list_index_notify_deinit(struct mailbox_list_notify *notify)
+{
+	struct mailbox_list_notify_index *inotify =
+		(struct mailbox_list_notify_index *)notify;
+	bool b;
+
+	if (inotify->inbox != NULL)
+		mailbox_free(&inotify->inbox);
+	if (inotify->subscriptions != NULL)
+		mailbox_tree_deinit(&inotify->subscriptions);
+	io_remove(&inotify->io_wait);
+	io_remove(&inotify->io_wait_inbox);
+	timeout_remove(&inotify->to_wait);
+	timeout_remove(&inotify->to_notify);
+	if (inotify->sync_ctx != NULL)
+		(void)mail_index_view_sync_commit(&inotify->sync_ctx, &b);
+	mail_index_view_close(&inotify->view);
+	mail_index_view_close(&inotify->old_view);
+	mailbox_list_notify_tree_deinit(&inotify->tree);
+	array_free(&inotify->new_subscriptions);
+	array_free(&inotify->new_unsubscriptions);
+	array_free(&inotify->new_uids);
+	array_free(&inotify->expunged_uids);
+	array_free(&inotify->changed_uids);
+	array_free(&inotify->renames);
+	str_free(&inotify->rec_name);
+	i_free(inotify->list_log_path);
+	i_free(inotify->inbox_log_path);
+	i_free(inotify);
+}
+
+static struct mailbox_list_index_node *
+notify_lookup_guid(struct mailbox_list_notify_index *inotify,
+		   struct mail_index_view *view,
+		   uint32_t uid, enum mailbox_status_items items,
+		   struct mailbox_status *status_r, guid_128_t guid_r)
+{
+	struct mailbox_list_index *ilist =
+		INDEX_LIST_CONTEXT_REQUIRE(inotify->notify.list);
+	struct mailbox_list_index_node *index_node;
+	const char *reason;
+	uint32_t seq;
+
+	if (!mail_index_lookup_seq(view, uid, &seq))
+		return NULL;
+
+	index_node = mailbox_list_index_lookup_uid(ilist, uid);
+	if (index_node == NULL) {
+		/* re-parse the index list using the given view. we could be
+		   jumping here between old and new view. */
+		(void)mailbox_list_index_parse(inotify->notify.list,
+					       view, FALSE);
+		index_node = mailbox_list_index_lookup_uid(ilist, uid);
+		if (index_node == NULL)
+			return NULL;
+	}
+
+	/* get GUID */
+	i_zero(status_r);
+	memset(guid_r, 0, GUID_128_SIZE);
+	(void)mailbox_list_index_status(inotify->notify.list, view, seq,
+					items, status_r, guid_r, NULL, &reason);
+	return index_node;
+}
+
+static void notify_update_stat(struct mailbox_list_notify_index *inotify,
+			       bool stat_list, bool stat_inbox)
+{
+	bool call = FALSE;
+
+	if (stat_list &&
+	    stat(inotify->list_log_path, &inotify->list_last_st) < 0 &&
+	    errno != ENOENT) {
+		e_error(inotify->notify.list->ns->user->event,
+			"stat(%s) failed: %m", inotify->list_log_path);
+		call = TRUE;
+	}
+	if (inotify->inbox_log_path != NULL && stat_inbox) {
+		if (stat(inotify->inbox_log_path, &inotify->inbox_last_st) < 0 &&
+		    errno != ENOENT) {
+			e_error(inotify->notify.list->ns->user->event,
+				"stat(%s) failed: %m", inotify->inbox_log_path);
+			call = TRUE;
+		}
+	}
+	if (call)
+		mailbox_list_index_notify_wait(&inotify->notify, NULL, NULL);
+}
+
+static void
+mailbox_list_index_notify_sync_init(struct mailbox_list_notify_index *inotify)
+{
+	struct mail_index_view_sync_rec sync_rec;
+
+	notify_update_stat(inotify, TRUE, TRUE);
+	(void)mail_index_refresh(inotify->view->index);
+
+	/* sync the view so that map extensions gets updated */
+	inotify->sync_ctx = mail_index_view_sync_begin(inotify->view, 0);
+	mail_transaction_log_view_mark(inotify->view->log_view);
+	while (mail_index_view_sync_next(inotify->sync_ctx, &sync_rec)) ;
+	mail_transaction_log_view_rewind(inotify->view->log_view);
+
+	inotify->cur_ext = ILIST_EXT_NONE;
+	inotify->cur_ext_id = (uint32_t)-1;
+}
+
+static bool notify_ext_rec(struct mailbox_list_notify_index *inotify,
+			   uint32_t uid)
+{
+	struct mailbox_list_notify *notify = &inotify->notify;
+
+	switch (inotify->cur_ext) {
+	case ILIST_EXT_NONE:
+		i_unreached();
+	case ILIST_EXT_BASE:
+		/* UIDVALIDITY changed */
+		if ((notify->mask & MAILBOX_LIST_NOTIFY_UIDVALIDITY) == 0)
+			return FALSE;
+		break;
+	case ILIST_EXT_MSGS:
+		/* APPEND, EXPUNGE, \Seen or \Recent flag change */
+		if ((notify->mask & MAILBOX_LIST_NOTIFY_STATUS) == 0)
+			return FALSE;
+		break;
+	case ILIST_EXT_HIGHESTMODSEQ:
+		/* when this doesn't come with EXT_MSGS update,
+		   it can only be a flag change or an explicit
+		   modseq change */
+		if ((notify->mask & MAILBOX_LIST_NOTIFY_MODSEQ_CHANGES) == 0)
+			return FALSE;
+		break;
+	case ILIST_EXT_UNKNOWN:
+		return FALSE;
+	}
+	seq_range_array_add(&inotify->changed_uids, uid);
+	return TRUE;
+}
+
+static int
+mailbox_list_index_notify_read_next(struct mailbox_list_notify_index *inotify)
+{
+	struct mailbox_list_notify *notify = &inotify->notify;
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(notify->list);
+	const struct mail_transaction_header *hdr;
+	const void *data;
+	int ret;
+
+	ret = mail_transaction_log_view_next(inotify->view->log_view,
+					     &hdr, &data);
+	if (ret <= 0)
+		return ret;
+
+	if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
+		/* all mailbox index updates are external */
+		return 1;
+	}
+	switch (hdr->type & MAIL_TRANSACTION_TYPE_MASK) {
+	case MAIL_TRANSACTION_APPEND: {
+		/* mailbox added or renamed */
+		const struct mail_index_record *rec, *end;
+
+		if ((notify->mask & (MAILBOX_LIST_NOTIFY_CREATE |
+				     MAILBOX_LIST_NOTIFY_RENAME)) == 0)
+			break;
+
+		end = CONST_PTR_OFFSET(data, hdr->size);
+		for (rec = data; rec != end; rec++)
+			seq_range_array_add(&inotify->new_uids, rec->uid);
+		break;
+	}
+	case MAIL_TRANSACTION_EXPUNGE_GUID: {
+		/* mailbox deleted or renamed */
+		const struct mail_transaction_expunge_guid *rec, *end;
+
+		if ((notify->mask & (MAILBOX_LIST_NOTIFY_DELETE |
+				     MAILBOX_LIST_NOTIFY_RENAME)) == 0)
+			break;
+
+		end = CONST_PTR_OFFSET(data, hdr->size);
+		for (rec = data; rec != end; rec++)
+			seq_range_array_add(&inotify->expunged_uids, rec->uid);
+		break;
+	}
+	case MAIL_TRANSACTION_EXT_INTRO: {
+		struct mail_index_map *map = inotify->view->map;
+		const struct mail_transaction_ext_intro *rec = data;
+		const struct mail_index_ext *ext = NULL;
+		const char *name;
+		uint32_t ext_map_idx;
+
+		if (!array_is_created(&map->extensions))
+			break;
+		/* we want to know what extension the future
+		   ext-rec-updates are changing. we're assuming here that
+		   there is only one ext-intro record before those,
+		   which is true at least for now. */
+		if (rec->ext_id != (uint32_t)-1 &&
+		    rec->ext_id < array_count(&map->extensions)) {
+			/* get extension by id */
+			ext = array_idx(&map->extensions, rec->ext_id);
+		} else if (rec->name_size > 0) {
+			/* by name */
+			name = t_strndup(rec+1, rec->name_size);
+			if (mail_index_map_lookup_ext(map, name, &ext_map_idx))
+				ext = array_idx(&map->extensions, ext_map_idx);
+		}
+		if (ext != NULL) {
+			if (ext->index_idx == ilist->ext_id)
+				inotify->cur_ext = ILIST_EXT_BASE;
+			else if (ext->index_idx == ilist->msgs_ext_id)
+				inotify->cur_ext = ILIST_EXT_MSGS;
+			else if (ext->index_idx == ilist->hmodseq_ext_id)
+				inotify->cur_ext = ILIST_EXT_HIGHESTMODSEQ;
+			else
+				inotify->cur_ext = ILIST_EXT_UNKNOWN;
+			inotify->cur_ext_id = ext->index_idx;
+		}
+		break;
+	}
+	case MAIL_TRANSACTION_EXT_REC_UPDATE: {
+		const struct mail_index_registered_ext *ext;
+		const struct mail_transaction_ext_rec_update *rec;
+		unsigned int i, record_size;
+
+		if (inotify->cur_ext == ILIST_EXT_NONE) {
+			e_error(ilist->index->event,
+				"%s: Missing ext-intro for ext-rec-update",
+				ilist->index->filepath);
+			break;
+		}
+
+		/* the record is padded to 32bits in the transaction log */
+		ext = array_idx(&inotify->view->index->extensions,
+				inotify->cur_ext_id);
+		record_size = (sizeof(*rec) + ext->record_size + 3) & ~3U;
+		for (i = 0; i < hdr->size; i += record_size) {
+			rec = CONST_PTR_OFFSET(data, i);
+
+			if (i + record_size > hdr->size)
+				break;
+			if (!notify_ext_rec(inotify, rec->uid))
+				break;
+		}
+		break;
+	}
+	}
+	return 1;
+}
+
+static int
+mailbox_list_inotify_entry_guid_cmp(const struct mailbox_list_inotify_entry *r1,
+				    const struct mailbox_list_inotify_entry *r2)
+{
+	int ret;
+
+	ret = memcmp(r1->guid, r2->guid, sizeof(r1->guid));
+	if (ret != 0)
+		return ret;
+
+	if (r1->expunge == r2->expunge) {
+		/* this really shouldn't happen */
+		return 0;
+	}
+	return r1->expunge ? -1 : 1;
+}
+
+static void
+mailbox_list_index_notify_find_renames(struct mailbox_list_notify_index *inotify)
+{
+	ARRAY(struct mailbox_list_inotify_entry) entries;
+	struct mailbox_status status;
+	struct mailbox_list_notify_rename *rename;
+	struct mailbox_list_inotify_entry *entry;
+	const struct mailbox_list_inotify_entry *e;
+	unsigned int i, count;
+	guid_128_t guid;
+	uint32_t uid;
+
+	/* first get all of the added and expunged GUIDs */
+	t_array_init(&entries, array_count(&inotify->new_uids) +
+		     array_count(&inotify->expunged_uids));
+	while (seq_range_array_iter_nth(&inotify->expunged_uids_iter,
+					inotify->expunged_uids_n++, &uid)) {
+		if (notify_lookup_guid(inotify, inotify->old_view, uid,
+				       0, &status, guid) != NULL &&
+		    !guid_128_is_empty(guid)) {
+			entry = array_append_space(&entries);
+			entry->uid = uid;
+			entry->expunge = TRUE;
+			memcpy(entry->guid, guid, sizeof(entry->guid));
+		}
+	}
+
+	(void)mailbox_list_index_parse(inotify->notify.list,
+				       inotify->view, TRUE);
+	while (seq_range_array_iter_nth(&inotify->new_uids_iter,
+					inotify->new_uids_n++, &uid)) {
+		if (notify_lookup_guid(inotify, inotify->view, uid,
+				       0, &status, guid) != NULL &&
+		    !guid_128_is_empty(guid)) {
+			entry = array_append_space(&entries);
+			entry->uid = uid;
+			memcpy(entry->guid, guid, sizeof(entry->guid));
+		}
+	}
+
+	/* now sort the entries by GUID and find those that have been both
+	   added and expunged */
+	array_sort(&entries, mailbox_list_inotify_entry_guid_cmp);
+
+	e = array_get(&entries, &count);
+	for (i = 1; i < count; i++) {
+		if (e[i-1].expunge && !e[i].expunge &&
+		    memcmp(e[i-1].guid, e[i].guid, sizeof(e[i].guid)) == 0) {
+			rename = array_append_space(&inotify->renames);
+			rename->old_uid = e[i-1].uid;
+			rename->new_uid = e[i].uid;
+
+			seq_range_array_remove(&inotify->expunged_uids,
+					       rename->old_uid);
+			seq_range_array_remove(&inotify->new_uids,
+					       rename->new_uid);
+		}
+	}
+}
+
+static void
+mailbox_list_index_notify_find_subscribes(struct mailbox_list_notify_index *inotify)
+{
+	struct mailbox_tree_iterate_context *old_iter, *new_iter;
+	struct mailbox_tree_context *old_tree, *new_tree;
+	const char *old_path = NULL, *new_path = NULL;
+	pool_t pool;
+	int ret;
+
+	if (mailbox_list_iter_subscriptions_refresh(inotify->notify.list) < 0)
+		return;
+	mailbox_tree_sort(inotify->notify.list->subscriptions);
+
+	old_tree = inotify->subscriptions;
+	new_tree = mailbox_tree_dup(inotify->notify.list->subscriptions);
+
+	old_iter = mailbox_tree_iterate_init(old_tree, NULL, MAILBOX_SUBSCRIBED);
+	new_iter = mailbox_tree_iterate_init(new_tree, NULL, MAILBOX_SUBSCRIBED);
+
+	pool = mailbox_tree_get_pool(new_tree);
+	for (;;) {
+		if (old_path == NULL) {
+			if (mailbox_tree_iterate_next(old_iter, &old_path) == NULL)
+				old_path = NULL;
+		}
+		if (new_path == NULL) {
+			if (mailbox_tree_iterate_next(new_iter, &new_path) == NULL)
+				new_path = NULL;
+		}
+
+		if (old_path == NULL) {
+			if (new_path == NULL)
+				break;
+			ret = 1;
+		} else if (new_path == NULL)
+			ret = -1;
+		else {
+			ret = strcmp(old_path, new_path);
+		}
+
+		if (ret == 0) {
+			old_path = NULL;
+			new_path = NULL;
+		} else if (ret > 0) {
+			new_path = p_strdup(pool, new_path);
+			array_push_back(&inotify->new_subscriptions,
+					&new_path);
+			new_path = NULL;
+		} else {
+			old_path = p_strdup(pool, old_path);
+			array_push_back(&inotify->new_unsubscriptions,
+					&old_path);
+			old_path = NULL;
+		}
+	}
+	mailbox_tree_iterate_deinit(&old_iter);
+	mailbox_tree_iterate_deinit(&new_iter);
+
+	mailbox_tree_deinit(&inotify->subscriptions);
+	inotify->subscriptions = new_tree;
+}
+
+static void
+mailbox_list_index_notify_reset_iters(struct mailbox_list_notify_index *inotify)
+{
+	seq_range_array_iter_init(&inotify->new_uids_iter,
+				  &inotify->new_uids);
+	seq_range_array_iter_init(&inotify->expunged_uids_iter,
+				  &inotify->expunged_uids);
+	seq_range_array_iter_init(&inotify->changed_uids_iter,
+				  &inotify->changed_uids);
+	inotify->changed_uids_n = 0;
+	inotify->new_uids_n = 0;
+	inotify->expunged_uids_n = 0;
+	inotify->rename_idx = 0;
+	inotify->subscription_idx = 0;
+	inotify->unsubscription_idx = 0;
+}
+
+static void
+mailbox_list_index_notify_read_init(struct mailbox_list_notify_index *inotify)
+{
+	bool b;
+	int ret;
+
+	mailbox_list_index_notify_sync_init(inotify);
+
+	/* read all changes from .log file */
+	while ((ret = mailbox_list_index_notify_read_next(inotify)) > 0) ;
+	inotify->read_failed = ret < 0;
+
+	(void)mail_index_view_sync_commit(&inotify->sync_ctx, &b);
+
+	/* remove changes for already deleted mailboxes */
+	seq_range_array_remove_seq_range(&inotify->new_uids,
+					 &inotify->expunged_uids);
+	seq_range_array_remove_seq_range(&inotify->changed_uids,
+					 &inotify->expunged_uids);
+	mailbox_list_index_notify_reset_iters(inotify);
+	if (array_count(&inotify->new_uids) > 0 &&
+	    array_count(&inotify->expunged_uids) > 0) {
+		mailbox_list_index_notify_find_renames(inotify);
+		mailbox_list_index_notify_reset_iters(inotify);
+	}
+	if (inotify->subscriptions != NULL)
+		mailbox_list_index_notify_find_subscribes(inotify);
+
+	inotify->initialized = TRUE;
+}
+
+static void
+mailbox_list_index_notify_read_deinit(struct mailbox_list_notify_index *inotify)
+{
+	/* save the old view so we can look up expunged records */
+	mail_index_view_close(&inotify->old_view);
+	inotify->old_view = mail_index_view_dup_private(inotify->view);
+
+	array_clear(&inotify->new_subscriptions);
+	array_clear(&inotify->new_unsubscriptions);
+	array_clear(&inotify->new_uids);
+	array_clear(&inotify->expunged_uids);
+	array_clear(&inotify->changed_uids);
+	array_clear(&inotify->renames);
+
+	inotify->initialized = FALSE;
+}
+
+static bool
+mailbox_list_index_notify_lookup(struct mailbox_list_notify_index *inotify,
+				 struct mail_index_view *view,
+				 uint32_t uid, enum mailbox_status_items items,
+				 struct mailbox_status *status_r,
+				 struct mailbox_list_notify_rec **rec_r)
+{
+	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
+	struct mailbox_list_index_node *index_node;
+	const char *storage_name;
+	char ns_sep = mailbox_list_get_hierarchy_sep(inotify->notify.list);
+
+	i_zero(rec);
+	index_node = notify_lookup_guid(inotify, view, uid,
+					items, status_r, rec->guid);
+	if (index_node == NULL)
+		return FALSE;
+
+	/* get storage_name */
+	str_truncate(inotify->rec_name, 0);
+	mailbox_list_index_node_get_path(index_node, ns_sep, inotify->rec_name);
+	storage_name = str_c(inotify->rec_name);
+
+	rec->storage_name = storage_name;
+	rec->vname = mailbox_list_get_vname(inotify->notify.list,
+					    rec->storage_name);
+	*rec_r = rec;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_rename(struct mailbox_list_notify_index *inotify,
+				 unsigned int idx)
+{
+	const struct mailbox_list_notify_rename *rename;
+	struct mailbox_list_notify_rec *rec;
+	struct mailbox_status status;
+	const char *old_vname;
+
+	rename = array_idx(&inotify->renames, idx);
+
+	/* lookup the old name */
+	if (!mailbox_list_index_notify_lookup(inotify, inotify->old_view,
+					      rename->old_uid, 0, &status, &rec))
+		return FALSE;
+	old_vname = t_strdup(rec->vname);
+
+	/* return using the new name */
+	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
+					      rename->new_uid, 0, &status, &rec))
+		return FALSE;
+
+	rec->old_vname = old_vname;
+	rec->events = MAILBOX_LIST_NOTIFY_RENAME;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_subscribe(struct mailbox_list_notify_index *inotify,
+				    unsigned int idx)
+{
+	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
+
+	i_zero(rec);
+	rec->vname = array_idx_elem(&inotify->new_subscriptions, idx);
+	rec->storage_name = mailbox_list_get_storage_name(inotify->notify.list,
+							  rec->vname);
+	rec->events = MAILBOX_LIST_NOTIFY_SUBSCRIBE;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_unsubscribe(struct mailbox_list_notify_index *inotify,
+				      unsigned int idx)
+{
+	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
+
+	i_zero(rec);
+	rec->vname = array_idx_elem(&inotify->new_unsubscriptions, idx);
+	rec->storage_name = mailbox_list_get_storage_name(inotify->notify.list,
+							  rec->vname);
+	rec->events = MAILBOX_LIST_NOTIFY_UNSUBSCRIBE;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_expunge(struct mailbox_list_notify_index *inotify,
+				  uint32_t uid)
+{
+	struct mailbox_list_notify_rec *rec;
+	struct mailbox_status status;
+
+	if (!mailbox_list_index_notify_lookup(inotify, inotify->old_view,
+					      uid, 0, &status, &rec))
+		return FALSE;
+	rec->events = MAILBOX_LIST_NOTIFY_DELETE;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_new(struct mailbox_list_notify_index *inotify,
+			      uint32_t uid)
+{
+	struct mailbox_list_notify_rec *rec;
+	struct mailbox_status status;
+
+	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
+					      uid, 0, &status, &rec))
+		i_unreached();
+	rec->events = MAILBOX_LIST_NOTIFY_CREATE;
+	return TRUE;
+}
+
+static bool
+mailbox_list_index_notify_change(struct mailbox_list_notify_index *inotify,
+				 uint32_t uid)
+{
+	struct mailbox_list_notify_rec *rec;
+	struct mailbox_notify_node *nnode, empty_node;
+	struct mailbox_status status;
+
+	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
+					      uid, notify_status_items,
+					      &status, &rec)) {
+		/* Mailbox is already deleted. We won't get here if we're
+		   tracking MAILBOX_LIST_NOTIFY_DELETE or _RENAME
+		   (which update expunged_uids). */
+		return FALSE;
+	}
+
+	/* get the old status */
+	nnode = mailbox_list_notify_tree_lookup(inotify->tree,
+						rec->storage_name);
+	if (nnode == NULL) {
+		/* mailbox didn't exist earlier - report all events as new */
+		i_zero(&empty_node);
+		nnode = &empty_node;
+	}
+	rec->events |= mailbox_list_index_get_changed_events(nnode, &status);
+	/* update internal state */
+	mailbox_notify_node_update_status(nnode, &status);
+	return rec->events != 0;
+}
+
+static bool
+mailbox_list_index_notify_try_next(struct mailbox_list_notify_index *inotify)
+{
+	uint32_t uid;
+
+	/* first show mailbox deletes */
+	if (seq_range_array_iter_nth(&inotify->expunged_uids_iter,
+				     inotify->expunged_uids_n++, &uid))
+		return mailbox_list_index_notify_expunge(inotify, uid);
+
+	/* mailbox renames */
+	if (inotify->rename_idx < array_count(&inotify->renames)) {
+		return mailbox_list_index_notify_rename(inotify,
+							inotify->rename_idx++);
+	}
+
+	/* next mailbox creates */
+	if (seq_range_array_iter_nth(&inotify->new_uids_iter,
+				     inotify->new_uids_n++, &uid))
+		return mailbox_list_index_notify_new(inotify, uid);
+
+	/* subscribes */
+	if (inotify->subscription_idx < array_count(&inotify->new_subscriptions)) {
+		return mailbox_list_index_notify_subscribe(inotify,
+					inotify->subscription_idx++);
+	}
+	if (inotify->unsubscription_idx < array_count(&inotify->new_unsubscriptions)) {
+		return mailbox_list_index_notify_unsubscribe(inotify,
+					inotify->unsubscription_idx++);
+	}
+
+	/* STATUS updates */
+	while (seq_range_array_iter_nth(&inotify->changed_uids_iter,
+					inotify->changed_uids_n++, &uid)) {
+		if (mailbox_list_index_notify_change(inotify, uid))
+			return TRUE;
+	}
+	return FALSE;
+}
+
+static enum mailbox_list_notify_event
+mailbox_list_notify_inbox_get_events(struct mailbox_list_notify_index *inotify)
+{
+	struct mailbox_status old_status, new_status;
+	struct mailbox_notify_node old_nnode;
+
+	mailbox_get_open_status(inotify->inbox, notify_status_items, &old_status);
+	if (mailbox_sync(inotify->inbox, MAILBOX_SYNC_FLAG_FAST) < 0) {
+		e_error(inotify->notify.list->ns->user->event,
+			"Mailbox list index notify: Failed to sync INBOX: %s",
+			mailbox_get_last_internal_error(inotify->inbox, NULL));
+		return 0;
+	}
+	mailbox_get_open_status(inotify->inbox, notify_status_items, &new_status);
+
+	mailbox_notify_node_update_status(&old_nnode, &old_status);
+	return mailbox_list_index_get_changed_events(&old_nnode, &new_status);
+}
+
+int mailbox_list_index_notify_next(struct mailbox_list_notify *notify,
+				   const struct mailbox_list_notify_rec **rec_r)
+{
+	struct mailbox_list_notify_index *inotify =
+		(struct mailbox_list_notify_index *)notify;
+
+	if (!inotify->initialized)
+		mailbox_list_index_notify_read_init(inotify);
+	if (mailbox_list_index_handle_corruption(notify->list) < 0)
+		return -1;
+
+	while (mailbox_list_index_notify_try_next(inotify)) {
+		if ((inotify->notify_rec.events & inotify->notify.mask) != 0) {
+			*rec_r = &inotify->notify_rec;
+			return 1;
+		} else {
+			/* caller doesn't care about this change */
+		}
+	}
+	if (inotify->inbox_event_pending) {
+		inotify->inbox_event_pending = FALSE;
+		i_zero(&inotify->notify_rec);
+		inotify->notify_rec.vname = "INBOX";
+		inotify->notify_rec.storage_name = "INBOX";
+		inotify->notify_rec.events =
+			mailbox_list_notify_inbox_get_events(inotify);
+		*rec_r = &inotify->notify_rec;
+		return 1;
+	}
+
+	mailbox_list_index_notify_read_deinit(inotify);
+	return inotify->read_failed ? -1 : 0;
+}
+
+static void notify_now_callback(struct mailbox_list_notify_index *inotify)
+{
+	timeout_remove(&inotify->to_notify);
+	inotify->wait_callback(inotify->wait_context);
+}
+
+static void list_notify_callback(struct mailbox_list_notify_index *inotify)
+{
+	struct stat list_prev_st = inotify->list_last_st;
+
+	if (inotify->to_notify != NULL) {
+		/* there's a pending notification already -
+		   no need to stat() again */
+		return;
+	}
+
+	notify_update_stat(inotify, TRUE, FALSE);
+	if (ST_CHANGED(inotify->list_last_st, list_prev_st)) {
+		/* log has changed. call the callback with a small delay
+		   to allow bundling multiple changes together */
+		inotify->to_notify =
+			timeout_add_short(NOTIFY_DELAY_MSECS,
+					  notify_now_callback, inotify);
+	}
+}
+
+static void inbox_notify_callback(struct mailbox_list_notify_index *inotify)
+{
+	struct stat inbox_prev_st = inotify->inbox_last_st;
+
+	if (inotify->to_notify != NULL && inotify->inbox_event_pending) {
+		/* there's a pending INBOX notification already -
+		   no need to stat() again */
+		return;
+	}
+
+	notify_update_stat(inotify, FALSE, TRUE);
+	if (ST_CHANGED(inotify->inbox_last_st, inbox_prev_st))
+		inotify->inbox_event_pending = TRUE;
+	if (inotify->inbox_event_pending && inotify->to_notify == NULL) {
+		/* log has changed. call the callback with a small delay
+		   to allow bundling multiple changes together */
+		inotify->to_notify =
+			timeout_add_short(NOTIFY_DELAY_MSECS,
+					  notify_now_callback, inotify);
+	}
+}
+
+static void full_notify_callback(struct mailbox_list_notify_index *inotify)
+{
+	list_notify_callback(inotify);
+	inbox_notify_callback(inotify);
+}
+
+void mailbox_list_index_notify_wait(struct mailbox_list_notify *notify,
+				    void (*callback)(void *context),
+				    void *context)
+{
+	struct mailbox_list_notify_index *inotify =
+		(struct mailbox_list_notify_index *)notify;
+	unsigned int check_interval;
+
+	inotify->wait_callback = callback;
+	inotify->wait_context = context;
+
+	if (callback == NULL) {
+		io_remove(&inotify->io_wait);
+		io_remove(&inotify->io_wait_inbox);
+		timeout_remove(&inotify->to_wait);
+		timeout_remove(&inotify->to_notify);
+	} else if (inotify->to_wait == NULL) {
+		(void)io_add_notify(inotify->list_log_path, list_notify_callback,
+				    inotify, &inotify->io_wait);
+		/* we need to check for INBOX explicitly, because INBOX changes
+		   don't get added to mailbox.list.index.log */
+		if (inotify->inbox_log_path != NULL) {
+			(void)io_add_notify(inotify->inbox_log_path,
+					    inbox_notify_callback, inotify,
+					    &inotify->io_wait_inbox);
+		}
+		/* check with timeout as well, in case io_add_notify()
+		   doesn't work (e.g. NFS) */
+		check_interval = notify->list->mail_set->mailbox_idle_check_interval;
+		i_assert(check_interval > 0);
+		inotify->to_wait = timeout_add(check_interval * 1000,
+					       full_notify_callback, inotify);
+		notify_update_stat(inotify, TRUE, TRUE);
+	}
+}
+
+void mailbox_list_index_notify_flush(struct mailbox_list_notify *notify)
+{
+	struct mailbox_list_notify_index *inotify =
+		(struct mailbox_list_notify_index *)notify;
+
+	if (inotify->to_notify == NULL &&
+	    notify->list->mail_set->mailbox_idle_check_interval > 0) {
+		/* no pending notification - check if anything had changed */
+		full_notify_callback(inotify);
+	}
+	if (inotify->to_notify != NULL)
+		notify_now_callback(inotify);
+}
diff --git a/src/lib-storage/list/mailbox-list-index-status.c b/src/lib-storage/list/mailbox-list-index-status.c
new file mode 100644
index 0000000..4218ae7
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-status.c
@@ -0,0 +1,862 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "mail-index-modseq.h"
+#include "mailbox-list-index-storage.h"
+#include "mailbox-list-index.h"
+
+#define CACHED_STATUS_ITEMS \
+	(STATUS_MESSAGES | STATUS_UNSEEN | STATUS_RECENT | \
+	 STATUS_UIDNEXT | STATUS_UIDVALIDITY | STATUS_HIGHESTMODSEQ)
+
+struct index_list_changes {
+	struct mailbox_status status;
+	guid_128_t guid;
+	uint32_t seq;
+	struct mailbox_index_vsize vsize;
+	uint32_t first_uid;
+
+	bool rec_changed;
+	bool msgs_changed;
+	bool hmodseq_changed;
+	bool vsize_changed;
+	bool first_saved_changed;
+};
+
+struct index_list_storage_module index_list_storage_module =
+	MODULE_CONTEXT_INIT(&mail_storage_module_register);
+
+static int
+index_list_exists(struct mailbox *box, bool auto_boxes,
+		  enum mailbox_existence *existence_r)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	struct mail_index_view *view;
+	const struct mail_index_record *rec;
+	enum mailbox_list_index_flags flags;
+	uint32_t seq;
+
+	if (mailbox_list_index_view_open(box, FALSE, &view, &seq) <= 0) {
+		/* failure / not found. fallback to the real storage check
+		   just in case to see if the mailbox was just created. */
+		return ibox->module_ctx.super.
+			exists(box, auto_boxes, existence_r);
+	}
+	rec = mail_index_lookup(view, seq);
+	flags = rec->flags;
+	mail_index_view_close(&view);
+
+	if ((flags & MAILBOX_LIST_INDEX_FLAG_NONEXISTENT) != 0)
+		*existence_r = MAILBOX_EXISTENCE_NONE;
+	else if ((flags & MAILBOX_LIST_INDEX_FLAG_NOSELECT) != 0)
+		*existence_r = MAILBOX_EXISTENCE_NOSELECT;
+	else
+		*existence_r = MAILBOX_EXISTENCE_SELECT;
+	return 0;
+}
+
+bool mailbox_list_index_status(struct mailbox_list *list,
+			       struct mail_index_view *view,
+			       uint32_t seq, enum mailbox_status_items items,
+			       struct mailbox_status *status_r,
+			       uint8_t *mailbox_guid,
+			       struct mailbox_index_vsize *vsize_r,
+			       const char **reason_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	const void *data;
+	bool expunged;
+	const char *reason = NULL;
+
+	if ((items & STATUS_UIDVALIDITY) != 0 || mailbox_guid != NULL) {
+		const struct mailbox_list_index_record *rec;
+
+		mail_index_lookup_ext(view, seq, ilist->ext_id,
+				      &data, &expunged);
+		rec = data;
+		if (rec == NULL) {
+			if ((items & STATUS_UIDVALIDITY) != 0)
+				reason = "Record for UIDVALIDITY";
+			else
+				reason = "Record for GUID";
+		} else {
+			if ((items & STATUS_UIDVALIDITY) != 0 &&
+			    rec->uid_validity == 0)
+				reason = "UIDVALIDITY=0";
+			else
+				status_r->uidvalidity = rec->uid_validity;
+			if (mailbox_guid != NULL)
+				memcpy(mailbox_guid, rec->guid, GUID_128_SIZE);
+		}
+	}
+
+	if ((items & (STATUS_MESSAGES | STATUS_UNSEEN |
+		      STATUS_RECENT | STATUS_UIDNEXT)) != 0) {
+		const struct mailbox_list_index_msgs_record *rec;
+
+		mail_index_lookup_ext(view, seq, ilist->msgs_ext_id,
+				      &data, &expunged);
+		rec = data;
+		if (rec == NULL)
+			reason = "Record for message counts";
+		else if (rec->uidnext == 0) {
+			reason = "Empty record for message counts";
+		} else {
+			status_r->messages = rec->messages;
+			status_r->unseen = rec->unseen;
+			status_r->recent = rec->recent;
+			status_r->uidnext = rec->uidnext;
+		}
+	}
+	if ((items & STATUS_HIGHESTMODSEQ) != 0) {
+		const uint64_t *rec;
+
+		mail_index_lookup_ext(view, seq, ilist->hmodseq_ext_id,
+				      &data, &expunged);
+		rec = data;
+		if (rec == NULL)
+			reason = "Record for HIGHESTMODSEQ";
+		else if (*rec == 0)
+			reason = "HIGHESTMODSEQ=0";
+		else
+			status_r->highest_modseq = *rec;
+	}
+	if (vsize_r != NULL) {
+		mail_index_lookup_ext(view, seq, ilist->vsize_ext_id,
+				      &data, &expunged);
+		if (data == NULL)
+			reason = "Record for vsize";
+		else
+			memcpy(vsize_r, data, sizeof(*vsize_r));
+	}
+	*reason_r = reason;
+	return reason == NULL;
+}
+
+static int
+index_list_get_cached_status(struct mailbox *box,
+			     enum mailbox_status_items items,
+			     struct mailbox_status *status_r)
+{
+	struct mail_index_view *view;
+	const char *reason;
+	uint32_t seq;
+	int ret;
+
+	if (items == 0)
+		return 1;
+
+	if ((items & STATUS_UNSEEN) != 0 &&
+	    (mailbox_get_private_flags_mask(box) & MAIL_SEEN) != 0) {
+		/* can't get UNSEEN from list index, since each user has
+		   different \Seen flags */
+		return 0;
+	}
+
+	if ((ret = mailbox_list_index_view_open(box, TRUE, &view, &seq)) <= 0)
+		return ret;
+
+	ret = mailbox_list_index_status(box->list, view, seq, items,
+					status_r, NULL, NULL, &reason) ? 1 : 0;
+	if (ret == 0) {
+		e_debug(box->event,
+			"Couldn't get status items from mailbox list index: %s",
+			reason);
+	}
+	mail_index_view_close(&view);
+	return ret;
+}
+
+static int
+index_list_get_status(struct mailbox *box, enum mailbox_status_items items,
+		      struct mailbox_status *status_r)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if ((items & ENUM_NEGATE(CACHED_STATUS_ITEMS)) == 0 && !box->opened) {
+		if (index_list_get_cached_status(box, items, status_r) > 0)
+			return 0;
+		/* nonsynced / error, fallback to doing it the slow way */
+	}
+	return ibox->module_ctx.super.get_status(box, items, status_r);
+}
+
+/* Opportunistic function to see ïf we can extract guid from mailbox path */
+static bool index_list_get_guid_from_path(struct mailbox *box, guid_128_t guid_r)
+{
+	const char *path;
+	if (mailbox_get_path_to(box, MAILBOX_LIST_PATH_TYPE_MAILBOX, &path) <= 0)
+		return FALSE;
+	const char *ptr = strrchr(path, '/');
+	if (ptr == NULL)
+		return FALSE;
+	return guid_128_from_string(ptr + 1, guid_r) == 0;
+}
+
+static int
+index_list_get_cached_guid(struct mailbox *box, guid_128_t guid_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mailbox_status status;
+	struct mail_index_view *view;
+	const char *reason;
+	uint32_t seq;
+	int ret;
+
+	/* If using INDEX layout, try determine GUID from mailbox path */
+	if (!ilist->has_backing_store &&
+	    index_list_get_guid_from_path(box, guid_r))
+		return 1;
+
+	if (ilist->syncing) {
+		/* syncing wants to know the GUID for a new mailbox. */
+		return 0;
+	}
+
+	if ((ret = mailbox_list_index_view_open(box, FALSE, &view, &seq)) <= 0)
+		return ret;
+
+	ret = mailbox_list_index_status(box->list, view, seq, 0,
+					&status, guid_r, NULL, &reason) ? 1 : 0;
+	if (ret > 0 && guid_128_is_empty(guid_r)) {
+		reason = "GUID is empty";
+		ret = 0;
+	}
+	if (ret == 0) {
+		e_debug(box->event,
+			"Couldn't get GUID from mailbox list index: %s",
+			reason);
+	}
+	mail_index_view_close(&view);
+	return ret;
+}
+
+static int index_list_get_cached_vsize(struct mailbox *box, uoff_t *vsize_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mailbox_status status;
+	struct mailbox_index_vsize vsize;
+	struct mail_index_view *view;
+	const char *reason;
+	uint32_t seq;
+	int ret;
+
+	i_assert(!ilist->syncing);
+
+	if ((ret = mailbox_list_index_view_open(box, TRUE, &view, &seq)) <= 0)
+		return ret;
+
+	ret = mailbox_list_index_status(box->list, view, seq,
+					STATUS_MESSAGES | STATUS_UIDNEXT,
+					&status, NULL, &vsize, &reason) ? 1 : 0;
+	if (ret > 0 && status.messages == 0 && status.uidnext > 0) {
+		/* mailbox is empty. its size has to be zero, regardless of
+		   what the vsize header says. */
+		vsize.vsize = 0;
+	} else if (ret > 0 && (vsize.highest_uid + 1 != status.uidnext ||
+			       vsize.message_count != status.messages)) {
+		/* out of date vsize info */
+		reason = "out of date vsize info";
+		ret = 0;
+	}
+	if (ret > 0)
+		*vsize_r = vsize.vsize;
+	else if (ret == 0) {
+		e_debug(box->event,
+			"Couldn't get vsize from mailbox list index: %s",
+			reason);
+	}
+	mail_index_view_close(&view);
+	return ret;
+}
+
+static int
+index_list_get_cached_first_saved(struct mailbox *box,
+				  struct mailbox_index_first_saved *first_saved_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mail_index_view *view;
+	struct mailbox_status status;
+	const char *reason;
+	const void *data;
+	bool expunged;
+	uint32_t seq;
+	int ret;
+
+	i_zero(first_saved_r);
+
+	if ((ret = mailbox_list_index_view_open(box, TRUE, &view, &seq)) <= 0)
+		return ret;
+
+	mail_index_lookup_ext(view, seq, ilist->first_saved_ext_id,
+			      &data, &expunged);
+	if (data != NULL)
+		memcpy(first_saved_r, data, sizeof(*first_saved_r));
+	if (first_saved_r->timestamp != 0 && first_saved_r->uid == 0) {
+		/* mailbox was empty the last time we updated this.
+		   we'll need to verify if it still is. */
+		if (!mailbox_list_index_status(box->list, view, seq,
+					       STATUS_MESSAGES,
+					       &status, NULL, NULL, &reason) ||
+		    status.messages != 0)
+			first_saved_r->timestamp = 0;
+	}
+	mail_index_view_close(&view);
+	return first_saved_r->timestamp != 0 ? 1 : 0;
+}
+
+static int
+index_list_try_get_metadata(struct mailbox *box,
+			    enum mailbox_metadata_items items,
+			    struct mailbox_metadata *metadata_r)
+{
+	enum mailbox_metadata_items noncached_items;
+	int ret;
+
+	i_assert(metadata_r != NULL);
+
+	if (box->opened) {
+		/* if mailbox is already opened, don't bother using the values
+		   in mailbox list index. they have a higher chance of being
+		   wrong. */
+		return 0;
+	}
+	/* see if we have a chance of fulfilling this without opening
+	   the mailbox. */
+	noncached_items = items & ENUM_NEGATE(MAILBOX_METADATA_GUID |
+					      MAILBOX_METADATA_VIRTUAL_SIZE |
+					      MAILBOX_METADATA_FIRST_SAVE_DATE);
+	if ((noncached_items & MAILBOX_METADATA_PHYSICAL_SIZE) != 0 &&
+	    box->mail_vfuncs->get_physical_size ==
+	    box->mail_vfuncs->get_virtual_size)
+		noncached_items = items & ENUM_NEGATE(MAILBOX_METADATA_PHYSICAL_SIZE);
+
+	if (noncached_items != 0)
+		return 0;
+
+	if ((items & MAILBOX_METADATA_GUID) != 0) {
+		if ((ret = index_list_get_cached_guid(box, metadata_r->guid)) <= 0)
+			return ret;
+	}
+	if ((items & (MAILBOX_METADATA_VIRTUAL_SIZE |
+		      MAILBOX_METADATA_PHYSICAL_SIZE)) != 0) {
+		if ((ret = index_list_get_cached_vsize(box, &metadata_r->virtual_size)) <= 0)
+			return ret;
+		if ((items & MAILBOX_METADATA_PHYSICAL_SIZE) != 0)
+			metadata_r->physical_size = metadata_r->virtual_size;
+	}
+	if ((items & MAILBOX_METADATA_FIRST_SAVE_DATE) != 0) {
+		struct mailbox_index_first_saved first_saved;
+
+		/* start writing first_saved to mailbox list index if it wasn't
+		   there already. */
+		box->update_first_saved = TRUE;
+
+		if ((ret = index_list_get_cached_first_saved(box, &first_saved)) <= 0)
+			return ret;
+		metadata_r->first_save_date =
+			first_saved.timestamp == (uint32_t)-1 ? (time_t)-1 :
+			(time_t)first_saved.timestamp;
+	}
+	return 1;
+}
+
+static int
+index_list_get_metadata(struct mailbox *box,
+			enum mailbox_metadata_items items,
+			struct mailbox_metadata *metadata_r)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if (index_list_try_get_metadata(box, items, metadata_r) != 0)
+		return 0;
+	return ibox->module_ctx.super.get_metadata(box, items, metadata_r);
+}
+
+static void
+index_list_update_fill_vsize(struct mailbox *box,
+			     struct mail_index_view *view,
+			     struct index_list_changes *changes_r)
+{
+	const void *data;
+	size_t size;
+
+	mail_index_get_header_ext(view, box->vsize_hdr_ext_id,
+				  &data, &size);
+	if (size == sizeof(changes_r->vsize))
+		memcpy(&changes_r->vsize, data, sizeof(changes_r->vsize));
+}
+
+static bool
+index_list_update_fill_changes(struct mailbox *box,
+			       struct mail_index_view *list_view,
+			       struct index_list_changes *changes_r)
+{
+	struct mailbox_list_index_node *node;
+	struct mail_index_view *view;
+	const struct mail_index_header *hdr;
+	struct mailbox_metadata metadata;
+	uint32_t seq1, seq2;
+
+	i_zero(changes_r);
+
+	node = mailbox_list_index_lookup(box->list, box->name);
+	if (node == NULL)
+		return FALSE;
+	if (!mail_index_lookup_seq(list_view, node->uid, &changes_r->seq))
+		return FALSE;
+
+	/* get STATUS info using the latest data in index.
+	   note that for shared mailboxes (with private indexes) this
+	   also means that the unseen count is always the owner's
+	   count, not what exists in the private index. */
+	view = mail_index_view_open(box->index);
+	hdr = mail_index_get_header(view);
+
+	changes_r->status.messages = hdr->messages_count;
+	changes_r->status.unseen =
+		hdr->messages_count - hdr->seen_messages_count;
+	changes_r->status.uidvalidity = hdr->uid_validity;
+	changes_r->status.uidnext = hdr->next_uid;
+
+	if (!mail_index_lookup_seq_range(view, hdr->first_recent_uid,
+					 (uint32_t)-1, &seq1, &seq2))
+		changes_r->status.recent = 0;
+	else
+		changes_r->status.recent = seq2 - seq1 + 1;
+
+	changes_r->status.highest_modseq = mail_index_modseq_get_highest(view);
+	if (changes_r->status.highest_modseq == 0) {
+		/* modseqs not enabled yet, but we can't return 0 */
+		changes_r->status.highest_modseq = 1;
+	}
+	index_list_update_fill_vsize(box, view, changes_r);
+	mail_index_view_close(&view); hdr = NULL;
+
+	if (mailbox_get_metadata(box, MAILBOX_METADATA_GUID, &metadata) == 0)
+		memcpy(changes_r->guid, metadata.guid, sizeof(changes_r->guid));
+	return TRUE;
+}
+
+static void
+index_list_first_saved_update_changes(struct mailbox *box,
+				      struct mail_index_view *list_view,
+				      struct index_list_changes *changes)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mailbox_index_first_saved first_saved;
+	const void *data;
+	bool expunged;
+
+	mail_index_lookup_ext(list_view, changes->seq,
+			      ilist->first_saved_ext_id, &data, &expunged);
+	if (data == NULL)
+		i_zero(&first_saved);
+	else
+		memcpy(&first_saved, data, sizeof(first_saved));
+	if (mail_index_view_get_messages_count(box->view) > 0)
+		mail_index_lookup_uid(box->view, 1, &changes->first_uid);
+	if (first_saved.uid == 0 && first_saved.timestamp == 0) {
+		/* it's not in the index yet. we'll set it only if we've
+		   just called MAILBOX_METADATA_FIRST_SAVE_DATE. */
+		changes->first_saved_changed = box->update_first_saved;
+	} else {
+		changes->first_saved_changed =
+			changes->first_uid != first_saved.uid;
+	}
+}
+
+static bool
+index_list_has_changed(struct mailbox *box, struct mail_index_view *list_view,
+		       struct index_list_changes *changes)
+{
+	struct mailbox_status old_status;
+	struct mailbox_index_vsize old_vsize;
+	const char *reason;
+	guid_128_t old_guid;
+
+	i_zero(&old_status);
+	i_zero(&old_vsize);
+	memset(old_guid, 0, sizeof(old_guid));
+	(void)mailbox_list_index_status(box->list, list_view, changes->seq,
+					CACHED_STATUS_ITEMS,
+					&old_status, old_guid,
+					&old_vsize, &reason);
+
+	changes->rec_changed =
+		old_status.uidvalidity != changes->status.uidvalidity &&
+		changes->status.uidvalidity != 0;
+	if (!guid_128_equals(changes->guid, old_guid) &&
+	    !guid_128_is_empty(changes->guid))
+		changes->rec_changed = TRUE;
+
+	if (MAILBOX_IS_NEVER_IN_INDEX(box)) {
+		/* check only UIDVALIDITY and GUID changes for INBOX */
+		return changes->rec_changed;
+	}
+
+	changes->msgs_changed =
+		old_status.messages != changes->status.messages ||
+		old_status.unseen != changes->status.unseen ||
+		old_status.recent != changes->status.recent ||
+		old_status.uidnext != changes->status.uidnext;
+	/* update highest-modseq only if they're ever been used */
+	if (old_status.highest_modseq == changes->status.highest_modseq) {
+		changes->hmodseq_changed = FALSE;
+	} else {
+		changes->hmodseq_changed = TRUE;
+	}
+	if (memcmp(&old_vsize, &changes->vsize, sizeof(old_vsize)) != 0)
+		changes->vsize_changed = TRUE;
+	index_list_first_saved_update_changes(box, list_view, changes);
+
+	return changes->rec_changed || changes->msgs_changed ||
+		changes->hmodseq_changed || changes->vsize_changed ||
+		changes->first_saved_changed;
+}
+
+static void
+index_list_update_first_saved(struct mailbox *box,
+			      struct mail_index_transaction *list_trans,
+			      const struct index_list_changes *changes)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mailbox_transaction_context *t;
+	struct mail *mail;
+	struct mailbox_index_first_saved first_saved;
+	uint32_t seq, messages_count;
+	time_t save_date;
+	int ret = 0;
+
+	i_zero(&first_saved);
+	first_saved.timestamp = (uint32_t)-1;
+
+	if (changes->first_uid != 0) {
+		t = mailbox_transaction_begin(box, 0, __func__);
+		mail = mail_alloc(t, MAIL_FETCH_SAVE_DATE, NULL);
+		messages_count = mail_index_view_get_messages_count(box->view);
+		for (seq = 1; seq <= messages_count; seq++) {
+			mail_set_seq(mail, seq);
+			if (mail_get_save_date(mail, &save_date) >= 0) {
+				first_saved.uid = mail->uid;
+				first_saved.timestamp = save_date;
+				break;
+			}
+			if (mailbox_get_last_mail_error(box) != MAIL_ERROR_EXPUNGED) {
+				ret = -1;
+				break;
+			}
+		}
+		mail_free(&mail);
+		(void)mailbox_transaction_commit(&t);
+	}
+	if (ret == 0) {
+		mail_index_update_ext(list_trans, changes->seq,
+				      ilist->first_saved_ext_id,
+				      &first_saved, NULL);
+	}
+}
+
+
+static void
+index_list_update(struct mailbox *box, struct mail_index_view *list_view,
+		  struct mail_index_transaction *list_trans,
+		  const struct index_list_changes *changes)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+
+	if (changes->rec_changed) {
+		struct mailbox_list_index_record rec;
+		const void *old_data;
+		bool expunged;
+
+		mail_index_lookup_ext(list_view, changes->seq, ilist->ext_id,
+				      &old_data, &expunged);
+		i_assert(old_data != NULL);
+		memcpy(&rec, old_data, sizeof(rec));
+
+		if (changes->status.uidvalidity != 0)
+			rec.uid_validity = changes->status.uidvalidity;
+		if (!guid_128_is_empty(changes->guid))
+			memcpy(rec.guid, changes->guid, sizeof(rec.guid));
+		mail_index_update_ext(list_trans, changes->seq, ilist->ext_id,
+				      &rec, NULL);
+	}
+
+	if (changes->msgs_changed) {
+		struct mailbox_list_index_msgs_record msgs;
+
+		i_zero(&msgs);
+		msgs.messages = changes->status.messages;
+		msgs.unseen = changes->status.unseen;
+		msgs.recent = changes->status.recent;
+		msgs.uidnext = changes->status.uidnext;
+
+		mail_index_update_ext(list_trans, changes->seq,
+				      ilist->msgs_ext_id, &msgs, NULL);
+	}
+	if (changes->hmodseq_changed) {
+		mail_index_update_ext(list_trans, changes->seq,
+				      ilist->hmodseq_ext_id,
+				      &changes->status.highest_modseq, NULL);
+	}
+	if (changes->vsize_changed) {
+		mail_index_update_ext(list_trans, changes->seq,
+				      ilist->vsize_ext_id,
+				      &changes->vsize, NULL);
+	}
+	if (changes->first_saved_changed)
+		index_list_update_first_saved(box, list_trans, changes);
+}
+
+static int index_list_update_mailbox(struct mailbox *box)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mail_index_sync_ctx *list_sync_ctx;
+	struct mail_index_view *list_view;
+	struct mail_index_transaction *list_trans;
+	struct index_list_changes changes;
+	int ret;
+
+	i_assert(box->opened);
+
+	if (ilist->syncing || ilist->updating_status)
+		return 0;
+	if (box->deleting) {
+		/* don't update status info while mailbox is being deleted.
+		   especially not a good idea if we're rolling back a created
+		   mailbox that somebody else had just created */
+		return 0;
+	}
+
+	/* refresh the mailbox list index once. we can't do this again after
+	   locking, because it could trigger list syncing. */
+	(void)mailbox_list_index_refresh(box->list);
+
+	/* first do a quick check while unlocked to see if anything changes */
+	list_view = mail_index_view_open(ilist->index);
+	if (!index_list_update_fill_changes(box, list_view, &changes))
+		ret = -1;
+	else if (index_list_has_changed(box, list_view, &changes))
+		ret = 1;
+	else {
+		/* if backend state changed on the last check, update it here
+		   now. we probably don't need to bother checking again if the
+		   state had changed? */
+		ret = ilist->index_last_check_changed ? 1 : 0;
+	}
+	mail_index_view_close(&list_view);
+	if (ret <= 0) {
+		if (ret < 0)
+			mailbox_list_index_refresh_later(box->list);
+		return 0;
+	}
+
+	/* looks like there are some changes. now lock the list index and do
+	   the whole thing all over again while locked. this guarantees
+	   that we'll always write the latest state of the mailbox. */
+	if (mail_index_sync_begin(ilist->index, &list_sync_ctx,
+				  &list_view, &list_trans, 0) < 0) {
+		mailbox_set_index_error(box);
+		return -1;
+	}
+	/* refresh to latest state of the mailbox now that we're locked */
+	if (mail_index_refresh(box->index) < 0) {
+		mailbox_set_index_error(box);
+		mail_index_sync_rollback(&list_sync_ctx);
+		return -1;
+	}
+
+	if (!index_list_update_fill_changes(box, list_view, &changes))
+		mailbox_list_index_refresh_later(box->list);
+	else {
+		ilist->updating_status = TRUE;
+		if (index_list_has_changed(box, list_view, &changes))
+			index_list_update(box, list_view, list_trans, &changes);
+		if (box->v.list_index_update_sync != NULL &&
+		    !MAILBOX_IS_NEVER_IN_INDEX(box)) {
+			box->v.list_index_update_sync(box, list_trans,
+						      changes.seq);
+		}
+		ilist->updating_status = FALSE;
+	}
+
+	struct mail_index_sync_rec sync_rec;
+	while (mail_index_sync_next(list_sync_ctx, &sync_rec)) ;
+	if (mail_index_sync_commit(&list_sync_ctx) < 0) {
+		mailbox_set_index_error(box);
+		return -1;
+	}
+	ilist->index_last_check_changed = FALSE;
+	return 0;
+}
+
+void mailbox_list_index_update_mailbox_index(struct mailbox *box,
+					     const struct mailbox_update *update)
+{
+	struct mail_index_view *list_view;
+	struct mail_index_transaction *list_trans;
+	struct index_list_changes changes;
+	struct mailbox_status status;
+	const char *reason;
+	guid_128_t mailbox_guid;
+	bool guid_changed = FALSE;
+
+	i_zero(&changes);
+	/* update the mailbox list index even if it has some other pending
+	   changes. */
+	if (mailbox_list_index_view_open(box, FALSE, &list_view, &changes.seq) <= 0)
+		return;
+
+	guid_128_empty(mailbox_guid);
+	(void)mailbox_list_index_status(box->list, list_view, changes.seq,
+					CACHED_STATUS_ITEMS, &status,
+					mailbox_guid, NULL, &reason);
+
+	if (update->uid_validity != 0) {
+		changes.rec_changed = TRUE;
+		changes.status.uidvalidity = update->uid_validity;
+	}
+	if (!guid_128_equals(update->mailbox_guid, mailbox_guid) &&
+	    !guid_128_is_empty(update->mailbox_guid)) {
+		changes.rec_changed = TRUE;
+		memcpy(changes.guid, update->mailbox_guid, sizeof(changes.guid));
+		guid_changed = TRUE;
+	}
+	if (guid_changed ||
+	    update->uid_validity != 0 ||
+	    update->min_next_uid != 0 ||
+	    update->min_first_recent_uid != 0 ||
+	    update->min_highest_modseq != 0) {
+		/* reset status counters to 0. let the syncing later figure out
+		   their correct values. */
+		changes.msgs_changed = TRUE;
+		changes.hmodseq_changed = TRUE;
+	}
+	list_trans = mail_index_transaction_begin(list_view,
+					MAIL_INDEX_TRANSACTION_FLAG_EXTERNAL);
+	index_list_update(box, list_view, list_trans, &changes);
+	(void)mail_index_transaction_commit(&list_trans);
+	mail_index_view_close(&list_view);
+}
+
+void mailbox_list_index_status_sync_init(struct mailbox *box)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	const struct mail_index_header *hdr;
+
+	hdr = mail_index_get_header(box->view);
+	ibox->pre_sync_log_file_seq = hdr->log_file_seq;
+	ibox->pre_sync_log_file_head_offset = hdr->log_file_head_offset;
+}
+
+void mailbox_list_index_status_sync_deinit(struct mailbox *box)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	const struct mail_index_header *hdr;
+
+	hdr = mail_index_get_header(box->view);
+	if (!ilist->opened &&
+	    ibox->pre_sync_log_file_head_offset == hdr->log_file_head_offset &&
+	    ibox->pre_sync_log_file_seq == hdr->log_file_seq) {
+		/* List index isn't open and sync changed nothing.
+		   Don't bother opening the list index. */
+		return;
+	}
+
+	/* it probably doesn't matter much here if we push/pop the error,
+	   but might as well do it. */
+	mail_storage_last_error_push(mailbox_get_storage(box));
+	(void)index_list_update_mailbox(box);
+	mail_storage_last_error_pop(mailbox_get_storage(box));
+}
+
+static int
+index_list_transaction_commit(struct mailbox_transaction_context *t,
+			      struct mail_transaction_commit_changes *changes_r)
+{
+	struct mailbox *box = t->box;
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if (ibox->module_ctx.super.transaction_commit(t, changes_r) < 0)
+		return -1;
+	t = NULL;
+
+	/* check all changes here, because e.g. vsize update is _OTHERS */
+	if (changes_r->changes_mask == 0)
+		return 0;
+
+	/* this transaction commit may have been done in error handling path
+	   and the caller still wants to access the current error. make sure
+	   that whatever we do here won't change the error. */
+	mail_storage_last_error_push(mailbox_get_storage(box));
+	(void)index_list_update_mailbox(box);
+	mail_storage_last_error_pop(mailbox_get_storage(box));
+	return 0;
+}
+
+void mailbox_list_index_status_set_info_flags(struct mailbox *box, uint32_t uid,
+					      enum mailbox_info_flags *flags)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(box->list);
+	struct mail_index_view *view;
+	struct mailbox_status status;
+	const char *reason;
+	uint32_t seq;
+	int ret;
+
+	view = mail_index_view_open(ilist->index);
+	if (!mail_index_lookup_seq(view, uid, &seq)) {
+		/* our in-memory tree is out of sync */
+		ret = 1;
+	} else {
+		ret = box->v.list_index_has_changed == NULL ? 0 :
+			box->v.list_index_has_changed(box, view, seq, TRUE,
+						      &reason);
+	}
+
+	if (ret != 0) {
+		/* error / not up to date. don't waste time with it. */
+		mail_index_view_close(&view);
+		return;
+	}
+
+	status.recent = 0;
+	(void)mailbox_list_index_status(box->list, view, seq, STATUS_RECENT,
+					&status, NULL, NULL, &reason);
+	mail_index_view_close(&view);
+
+	if (status.recent != 0)
+		*flags |= MAILBOX_MARKED;
+	else
+		*flags |= MAILBOX_UNMARKED;
+}
+
+void mailbox_list_index_status_init_mailbox(struct mailbox_vfuncs *v)
+{
+	v->exists = index_list_exists;
+	v->get_status = index_list_get_status;
+	v->get_metadata = index_list_get_metadata;
+	v->transaction_commit = index_list_transaction_commit;
+}
+
+void mailbox_list_index_status_init_finish(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	ilist->msgs_ext_id = mail_index_ext_register(ilist->index, "msgs", 0,
+		sizeof(struct mailbox_list_index_msgs_record),
+		sizeof(uint32_t));
+
+	ilist->hmodseq_ext_id =
+		mail_index_ext_register(ilist->index, "hmodseq", 0,
+					sizeof(uint64_t), sizeof(uint64_t));
+	ilist->vsize_ext_id =
+		mail_index_ext_register(ilist->index, "vsize", 0,
+			sizeof(struct mailbox_index_vsize), sizeof(uint64_t));
+	ilist->first_saved_ext_id =
+		mail_index_ext_register(ilist->index, "1saved", 0,
+			sizeof(struct mailbox_index_first_saved), sizeof(uint32_t));
+}
diff --git a/src/lib-storage/list/mailbox-list-index-storage.h b/src/lib-storage/list/mailbox-list-index-storage.h
new file mode 100644
index 0000000..6aeec8c
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-storage.h
@@ -0,0 +1,21 @@
+#ifndef MAILBOX_LIST_INDEX_STORAGE_H
+#define MAILBOX_LIST_INDEX_STORAGE_H
+
+#include "mail-storage-private.h"
+
+#define INDEX_LIST_STORAGE_CONTEXT(obj) \
+	MODULE_CONTEXT_REQUIRE(obj, index_list_storage_module)
+
+struct index_list_mailbox {
+	union mailbox_module_context module_ctx;
+
+	uint32_t pre_sync_log_file_seq;
+	uoff_t pre_sync_log_file_head_offset;
+
+	bool have_backend:1;
+};
+
+extern MODULE_CONTEXT_DEFINE(index_list_storage_module,
+			     &mail_storage_module_register);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-index-sync.c b/src/lib-storage/list/mailbox-list-index-sync.c
new file mode 100644
index 0000000..2994bb8
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-sync.c
@@ -0,0 +1,521 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "hash.h"
+#include "str.h"
+#include "sort.h"
+#include "mail-index.h"
+#include "mail-storage.h"
+#include "mailbox-list-index-sync.h"
+
+static void
+node_lookup_guid(struct mailbox_list_index_sync_context *ctx,
+		 const struct mailbox_list_index_node *node, guid_128_t guid_r)
+{
+	struct mailbox *box;
+	struct mailbox_metadata metadata;
+	const char *vname;
+	string_t *str = t_str_new(128);
+	char ns_sep = mailbox_list_get_hierarchy_sep(ctx->list);
+
+	mailbox_list_index_node_get_path(node, ns_sep, str);
+
+	vname = mailbox_list_get_vname(ctx->list, str_c(str));
+	box = mailbox_alloc(ctx->list, vname, 0);
+	if (mailbox_get_metadata(box, MAILBOX_METADATA_GUID, &metadata) == 0)
+		memcpy(guid_r, metadata.guid, GUID_128_SIZE);
+	mailbox_free(&box);
+}
+
+static void
+node_add_to_index(struct mailbox_list_index_sync_context *ctx,
+		  const struct mailbox_list_index_node *node, uint32_t *seq_r)
+{
+	struct mailbox_list_index_record irec;
+	uint32_t seq;
+
+	i_zero(&irec);
+	irec.name_id = node->name_id;
+	if (node->parent != NULL)
+		irec.parent_uid = node->parent->uid;
+
+	/* get mailbox GUID if possible. we need to do this early in here to
+	   make mailbox rename detection work in NOTIFY */
+	if (ctx->syncing_list) T_BEGIN {
+		node_lookup_guid(ctx, node, irec.guid);
+	} T_END;
+
+	mail_index_append(ctx->trans, node->uid, &seq);
+	mail_index_update_flags(ctx->trans, seq, MODIFY_REPLACE,
+		(enum mail_flags)MAILBOX_LIST_INDEX_FLAG_NONEXISTENT);
+	mail_index_update_ext(ctx->trans, seq, ctx->ilist->ext_id, &irec, NULL);
+
+	*seq_r = seq;
+}
+
+static struct mailbox_list_index_node *
+mailbox_list_index_node_add(struct mailbox_list_index_sync_context *ctx,
+			    struct mailbox_list_index_node *parent,
+			    const char *name, uint32_t *seq_r)
+{
+	struct mailbox_list_index_node *node;
+	char *dup_name;
+	mailbox_list_name_unescape(&name, ctx->list->set.storage_name_escape_char);
+
+	node = p_new(ctx->ilist->mailbox_pool,
+		     struct mailbox_list_index_node, 1);
+	node->flags = MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+		MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS;
+	/* we don't bother doing name deduplication here, even though it would
+	   be possible. */
+	node->raw_name = dup_name = p_strdup(ctx->ilist->mailbox_pool, name);
+	node->name_id = ++ctx->ilist->highest_name_id;
+	node->uid = ctx->next_uid++;
+
+	if (parent != NULL) {
+		node->parent = parent;
+		node->next = parent->children;
+		parent->children = node;
+	} else {
+		node->next = ctx->ilist->mailbox_tree;
+		ctx->ilist->mailbox_tree = node;
+	}
+	hash_table_insert(ctx->ilist->mailbox_hash,
+			  POINTER_CAST(node->uid), node);
+	hash_table_insert(ctx->ilist->mailbox_names,
+			  POINTER_CAST(node->name_id), dup_name);
+
+	node_add_to_index(ctx, node, seq_r);
+	return node;
+}
+
+uint32_t mailbox_list_index_sync_name(struct mailbox_list_index_sync_context *ctx,
+				      const char *name,
+				      struct mailbox_list_index_node **node_r,
+				      bool *created_r)
+{
+	const char *const *path, *empty_path[] = { "", NULL };
+	struct mailbox_list_index_node *node, *parent;
+	unsigned int i;
+	uint32_t seq = 0;
+
+	path = *name == '\0' ? empty_path :
+		t_strsplit(name, ctx->sep);
+	/* find the last node that exists in the path */
+	node = ctx->ilist->mailbox_tree; parent = NULL;
+	for (i = 0; path[i] != NULL; i++) {
+		node = mailbox_list_index_node_find_sibling(ctx->list, node, path[i]);
+		if (node == NULL)
+			break;
+
+		node->flags |= MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS;
+		parent = node;
+		node = node->children;
+	}
+
+	node = parent;
+	if (path[i] == NULL) {
+		/* the entire path exists */
+		i_assert(node != NULL);
+		if (!mail_index_lookup_seq(ctx->view, node->uid, &seq))
+			i_panic("mailbox list index: lost uid=%u", node->uid);
+		*created_r = FALSE;
+	} else {
+		/* create missing parts of the path */
+		for (; path[i] != NULL; i++) {
+			node = mailbox_list_index_node_add(ctx, node, path[i],
+							   &seq);
+		}
+		*created_r = TRUE;
+	}
+
+	*node_r = node;
+	return seq;
+}
+
+static void
+get_existing_name_ids(ARRAY_TYPE(uint32_t) *ids,
+		      const struct mailbox_list_index_node *node)
+{
+	for (; node != NULL; node = node->next) {
+		if (node->children != NULL)
+			get_existing_name_ids(ids, node->children);
+		array_push_back(ids, &node->name_id);
+	}
+}
+
+static void
+mailbox_list_index_sync_names(struct mailbox_list_index_sync_context *ctx)
+{
+	struct mailbox_list_index *ilist = ctx->ilist;
+	ARRAY_TYPE(uint32_t) existing_name_ids;
+	buffer_t *hdr_buf;
+	const void *ext_data;
+	size_t ext_size;
+	const char *name;
+	uint32_t id, prev_id = 0;
+
+	/* get all existing name IDs sorted */
+	i_array_init(&existing_name_ids, 64);
+	get_existing_name_ids(&existing_name_ids, ilist->mailbox_tree);
+	array_sort(&existing_name_ids, uint32_cmp);
+
+	hdr_buf = buffer_create_dynamic(default_pool, 1024);
+	buffer_append_zero(hdr_buf, sizeof(struct mailbox_list_index_header));
+
+	/* add existing names to header (with deduplication) */
+	array_foreach_elem(&existing_name_ids, id) {
+		if (id != prev_id) {
+			buffer_append(hdr_buf, &id, sizeof(id));
+			name = hash_table_lookup(ilist->mailbox_names,
+						 POINTER_CAST(id));
+			i_assert(name != NULL);
+			buffer_append(hdr_buf, name, strlen(name) + 1);
+			prev_id = id;
+		}
+	}
+	buffer_append_zero(hdr_buf, sizeof(id));
+
+	/* make sure header size is ok in index and update it */
+	mail_index_get_header_ext(ctx->view, ilist->ext_id,
+				  &ext_data, &ext_size);
+	if (nearest_power(ext_size) != nearest_power(hdr_buf->used)) {
+		mail_index_ext_resize(ctx->trans, ilist->ext_id,
+				      nearest_power(hdr_buf->used),
+				      sizeof(struct mailbox_list_index_record),
+				      sizeof(uint32_t));
+	}
+	mail_index_update_header_ext(ctx->trans, ilist->ext_id,
+				     0, hdr_buf->data, hdr_buf->used);
+	buffer_free(&hdr_buf);
+	array_free(&existing_name_ids);
+}
+
+static void
+mailbox_list_index_node_clear_exists(struct mailbox_list_index_node *node)
+{
+	while (node != NULL) {
+		if (node->children != NULL)
+			mailbox_list_index_node_clear_exists(node->children);
+
+		node->flags &= ENUM_NEGATE(MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS);
+		node = node->next;
+	}
+}
+
+static void
+sync_expunge_nonexistent(struct mailbox_list_index_sync_context *sync_ctx,
+			 struct mailbox_list_index_node *node)
+{
+	uint32_t seq;
+
+	while (node != NULL) {
+		if (node->children != NULL)
+			sync_expunge_nonexistent(sync_ctx, node->children);
+
+		if ((node->flags & MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS) == 0) {
+			if (mail_index_lookup_seq(sync_ctx->view, node->uid,
+						  &seq))
+				mail_index_expunge(sync_ctx->trans, seq);
+			mailbox_list_index_node_unlink(sync_ctx->ilist, node);
+		}
+		node = node->next;
+	}
+}
+
+int mailbox_list_index_sync_begin(struct mailbox_list *list,
+				  struct mailbox_list_index_sync_context **sync_ctx_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_sync_context *sync_ctx;
+	struct mail_index_sync_ctx *index_sync_ctx;
+	struct mail_index_view *view;
+	struct mail_index_transaction *trans;
+	const struct mail_index_header *hdr;
+	bool fix_attempted = FALSE;
+
+	i_assert(!ilist->syncing);
+
+retry:
+	if (mailbox_list_index_index_open(list) < 0)
+		return -1;
+
+	if (mail_index_sync_begin(ilist->index, &index_sync_ctx, &view, &trans,
+				  MAIL_INDEX_SYNC_FLAG_AVOID_FLAG_UPDATES) < 0) {
+		mailbox_list_index_set_index_error(list);
+		return -1;
+	}
+	mailbox_list_index_reset(ilist);
+
+	/* re-parse mailbox list now that it's refreshed and locked */
+	if (mailbox_list_index_parse(list, view, TRUE) < 0) {
+		mail_index_sync_rollback(&index_sync_ctx);
+		return -1;
+	}
+	if (ilist->call_corruption_callback && !fix_attempted) {
+		/* unlock and resync the index */
+		mail_index_sync_rollback(&index_sync_ctx);
+		if (mailbox_list_index_handle_corruption(list) < 0)
+			return -1;
+		fix_attempted = TRUE;
+		goto retry;
+	}
+
+	sync_ctx = i_new(struct mailbox_list_index_sync_context, 1);
+	sync_ctx->list = list;
+	sync_ctx->ilist = ilist;
+	sync_ctx->sep[0] = mailbox_list_get_hierarchy_sep(list);
+	sync_ctx->orig_highest_name_id = ilist->highest_name_id;
+	sync_ctx->index_sync_ctx = index_sync_ctx;
+	sync_ctx->trans = trans;
+
+	hdr = mail_index_get_header(view);
+	sync_ctx->next_uid = hdr->next_uid;
+
+	if (hdr->uid_validity == 0) {
+		/* first time indexing, set uidvalidity */
+		uint32_t uid_validity = ioloop_time;
+
+		mail_index_update_header(trans,
+			offsetof(struct mail_index_header, uid_validity),
+			&uid_validity, sizeof(uid_validity), TRUE);
+	}
+	sync_ctx->view = mail_index_transaction_open_updated_view(trans);
+	ilist->sync_ctx = sync_ctx;
+	ilist->syncing = TRUE;
+
+	*sync_ctx_r = sync_ctx;
+	return 0;
+}
+
+static int
+mailbox_list_index_sync_list(struct mailbox_list_index_sync_context *sync_ctx)
+{
+	struct mailbox_list_iterate_context *iter;
+	const struct mailbox_info *info;
+	enum mailbox_list_index_flags flags;
+	const char *patterns[2];
+	struct mailbox_list_index_node *node;
+	uint32_t seq;
+	bool created;
+
+	/* clear EXISTS-flags, so after sync we know what can be expunged */
+	mailbox_list_index_node_clear_exists(sync_ctx->ilist->mailbox_tree);
+
+	/* don't include autocreated mailboxes in index until they're
+	   actually created. this index may be used by multiple users, so
+	   we also want to ignore ACLs here. */
+	patterns[0] = "*"; patterns[1] = NULL;
+	iter = sync_ctx->ilist->module_ctx.super.
+		iter_init(sync_ctx->list, patterns,
+			  MAILBOX_LIST_ITER_RAW_LIST |
+			  MAILBOX_LIST_ITER_NO_AUTO_BOXES);
+
+	sync_ctx->syncing_list = TRUE;
+	while ((info = sync_ctx->ilist->module_ctx.super.iter_next(iter)) != NULL) T_BEGIN {
+		flags = 0;
+		if ((info->flags & MAILBOX_NONEXISTENT) != 0)
+			flags |= MAILBOX_LIST_INDEX_FLAG_NONEXISTENT;
+		if ((info->flags & MAILBOX_NOSELECT) != 0)
+			flags |= MAILBOX_LIST_INDEX_FLAG_NOSELECT;
+		if ((info->flags & MAILBOX_NOINFERIORS) != 0)
+			flags |= MAILBOX_LIST_INDEX_FLAG_NOINFERIORS;
+
+		const char *name = mailbox_list_get_storage_name(info->ns->list,
+								 info->vname);
+		if (strcmp(name, "INBOX") == 0 &&
+		    strcmp(info->vname, "INBOX") != 0 &&
+		    (info->ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0) {
+			/* prefix/INBOX - don't override INBOX with this */
+		} else {
+			seq = mailbox_list_index_sync_name(sync_ctx, name,
+							   &node, &created);
+			node->flags = flags | MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS;
+			mail_index_update_flags(sync_ctx->trans, seq,
+						MODIFY_REPLACE,
+						(enum mail_flags)flags);
+		}
+	} T_END;
+	sync_ctx->syncing_list = FALSE;
+
+	if (sync_ctx->ilist->module_ctx.super.iter_deinit(iter) < 0)
+		return -1;
+
+	/* successfully listed everything, expunge any unseen mailboxes */
+	sync_expunge_nonexistent(sync_ctx, sync_ctx->ilist->mailbox_tree);
+	return 0;
+}
+
+static void
+mailbox_list_index_sync_update_hdr(struct mailbox_list_index_sync_context *sync_ctx)
+{
+	if (sync_ctx->orig_highest_name_id != sync_ctx->ilist->highest_name_id ||
+	    sync_ctx->ilist->corrupted_names_or_parents) {
+		/* new names added. this implicitly resets refresh flag */
+		T_BEGIN {
+			mailbox_list_index_sync_names(sync_ctx);
+		} T_END;
+		sync_ctx->ilist->corrupted_names_or_parents = FALSE;
+	} else if (mailbox_list_index_need_refresh(sync_ctx->ilist,
+						   sync_ctx->view)) {
+		/* we're synced, reset refresh flag */
+		struct mailbox_list_index_header new_hdr;
+
+		new_hdr.refresh_flag = 0;
+		mail_index_update_header_ext(sync_ctx->trans, sync_ctx->ilist->ext_id,
+			offsetof(struct mailbox_list_index_header, refresh_flag),
+			&new_hdr.refresh_flag, sizeof(new_hdr.refresh_flag));
+	}
+}
+
+static void
+mailbox_list_index_sync_update_corrupted_node(struct mailbox_list_index_sync_context *sync_ctx,
+					      struct mailbox_list_index_node *node)
+{
+	struct mailbox_list_index_record irec;
+	uint32_t seq;
+	const void *data;
+	bool expunged;
+
+	if (!mail_index_lookup_seq(sync_ctx->view, node->uid, &seq))
+		return;
+
+	if (node->corrupted_ext) {
+		mail_index_lookup_ext(sync_ctx->view, seq,
+				      sync_ctx->ilist->ext_id,
+				      &data, &expunged);
+		i_assert(data != NULL);
+
+		memcpy(&irec, data, sizeof(irec));
+		irec.name_id = node->name_id;
+		irec.parent_uid = node->parent == NULL ? 0 : node->parent->uid;
+		mail_index_update_ext(sync_ctx->trans, seq,
+				      sync_ctx->ilist->ext_id, &irec, NULL);
+		node->corrupted_ext = FALSE;
+	}
+	if (node->corrupted_flags) {
+		mail_index_update_flags(sync_ctx->trans, seq, MODIFY_REPLACE,
+					(enum mail_flags)node->flags);
+		node->corrupted_flags = FALSE;
+	} else if ((node->flags & MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME) != 0) {
+		/* rely on lib-index to drop unnecessary updates */
+		mail_index_update_flags(sync_ctx->trans, seq, MODIFY_ADD,
+			(enum mail_flags)MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME);
+	}
+}
+
+static void
+mailbox_list_index_sync_update_corrupted_nodes(struct mailbox_list_index_sync_context *sync_ctx,
+					       struct mailbox_list_index_node *node)
+{
+	for (; node != NULL; node = node->next) {
+		mailbox_list_index_sync_update_corrupted_node(sync_ctx, node);
+		mailbox_list_index_sync_update_corrupted_nodes(sync_ctx, node->children);
+	}
+}
+
+static void
+mailbox_list_index_sync_update_corrupted(struct mailbox_list_index_sync_context *sync_ctx)
+{
+	if (!sync_ctx->ilist->corrupted_names_or_parents)
+		return;
+
+	mailbox_list_index_sync_update_corrupted_nodes(sync_ctx,
+		sync_ctx->ilist->mailbox_tree);
+}
+
+int mailbox_list_index_sync_end(struct mailbox_list_index_sync_context **_sync_ctx,
+				bool success)
+{
+	struct mailbox_list_index_sync_context *sync_ctx = *_sync_ctx;
+	int ret;
+
+	*_sync_ctx = NULL;
+
+	if (success) {
+		mailbox_list_index_sync_update_corrupted(sync_ctx);
+		mailbox_list_index_sync_update_hdr(sync_ctx);
+	}
+	mail_index_view_close(&sync_ctx->view);
+
+	if (success) {
+		struct mail_index_sync_rec sync_rec;
+		while (mail_index_sync_next(sync_ctx->index_sync_ctx, &sync_rec)) ;
+		if ((ret = mail_index_sync_commit(&sync_ctx->index_sync_ctx)) < 0)
+			mailbox_list_index_set_index_error(sync_ctx->list);
+	} else {
+		mail_index_sync_rollback(&sync_ctx->index_sync_ctx);
+		ret = -1;
+	}
+	sync_ctx->ilist->syncing = FALSE;
+	sync_ctx->ilist->sync_ctx = NULL;
+	i_free(sync_ctx);
+	return ret;
+}
+
+int mailbox_list_index_sync(struct mailbox_list *list, bool refresh)
+{
+	struct mailbox_list_index_sync_context *sync_ctx;
+	int ret = 0;
+
+	if (mailbox_list_index_sync_begin(list, &sync_ctx) < 0)
+		return -1;
+
+	if (!sync_ctx->ilist->has_backing_store) {
+		/* no backing store - we have nothing to sync to */
+	} else if (refresh ||
+		   sync_ctx->ilist->call_corruption_callback ||
+		   sync_ctx->ilist->corrupted_names_or_parents ||
+		   sync_ctx->ilist->highest_name_id == 0 ||
+		   !sync_ctx->list->mail_set->mailbox_list_index_very_dirty_syncs) {
+		/* sync the index against the backing store */
+		ret = mailbox_list_index_sync_list(sync_ctx);
+	}
+	return mailbox_list_index_sync_end(&sync_ctx, ret == 0);
+}
+
+int mailbox_list_index_sync_delete(struct mailbox_list_index_sync_context *sync_ctx,
+				   const char *name, bool delete_selectable)
+{
+	struct mailbox_list_index_record rec;
+	struct mailbox_list_index_node *node;
+	const void *data;
+	bool expunged;
+	uint32_t seq;
+
+	node = mailbox_list_index_lookup(sync_ctx->list, name);
+	if (node == NULL) {
+		mailbox_list_set_error(sync_ctx->list, MAIL_ERROR_NOTFOUND,
+				       T_MAIL_ERR_MAILBOX_NOT_FOUND(name));
+		return -1;
+	}
+	if (!mail_index_lookup_seq(sync_ctx->view, node->uid, &seq))
+		i_panic("mailbox list index: lost uid=%u", node->uid);
+	if (delete_selectable) {
+		/* make it at least non-selectable */
+		node->flags = MAILBOX_LIST_INDEX_FLAG_NOSELECT;
+		mail_index_update_flags(sync_ctx->trans, seq, MODIFY_REPLACE,
+					(enum mail_flags)node->flags);
+
+		mail_index_lookup_ext(sync_ctx->view, seq,
+				      sync_ctx->ilist->ext_id,
+				      &data, &expunged);
+		i_assert(data != NULL && !expunged);
+		memcpy(&rec, data, sizeof(rec));
+		rec.uid_validity = 0;
+		i_zero(&rec.guid);
+		mail_index_update_ext(sync_ctx->trans, seq,
+				      sync_ctx->ilist->ext_id, &rec, NULL);
+	}
+	if (node->children != NULL) {
+		/* can't delete this directory before its children,
+		   but we may have made it non-selectable already */
+		return 0;
+	}
+
+	/* we can remove the entire node */
+	mail_index_expunge(sync_ctx->trans, seq);
+	mailbox_list_index_node_unlink(sync_ctx->ilist, node);
+	return 1;
+}
diff --git a/src/lib-storage/list/mailbox-list-index-sync.h b/src/lib-storage/list/mailbox-list-index-sync.h
new file mode 100644
index 0000000..db20244
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index-sync.h
@@ -0,0 +1,35 @@
+#ifndef MAILBOX_LIST_INDEX_SYNC_H
+#define MAILBOX_LIST_INDEX_SYNC_H
+
+#include "mailbox-list-index.h"
+
+struct mailbox_list_index_sync_context {
+	struct mailbox_list *list;
+	struct mailbox_list_index *ilist;
+	char sep[2];
+	uint32_t next_uid;
+	uint32_t orig_highest_name_id;
+
+	struct mail_index_sync_ctx *index_sync_ctx;
+	struct mail_index_view *view;
+	struct mail_index_transaction *trans;
+
+	bool syncing_list:1;
+};
+
+int mailbox_list_index_sync_begin(struct mailbox_list *list,
+				  struct mailbox_list_index_sync_context **sync_ctx_r);
+int mailbox_list_index_sync_end(struct mailbox_list_index_sync_context **_sync_ctx,
+				bool success);
+int mailbox_list_index_sync(struct mailbox_list *list, bool refresh);
+
+/* Add name to index, return seq in index. */
+uint32_t mailbox_list_index_sync_name(struct mailbox_list_index_sync_context *ctx,
+				      const char *name,
+				      struct mailbox_list_index_node **node_r,
+				      bool *created_r);
+
+int mailbox_list_index_sync_delete(struct mailbox_list_index_sync_context *sync_ctx,
+				   const char *name, bool delete_selectable);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-index.c b/src/lib-storage/list/mailbox-list-index.c
new file mode 100644
index 0000000..9c8a718
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index.c
@@ -0,0 +1,1234 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "hash.h"
+#include "str.h"
+#include "mail-index-view-private.h"
+#include "mail-storage-hooks.h"
+#include "mail-storage-private.h"
+#include "mailbox-list-index-storage.h"
+#include "mailbox-list-index-sync.h"
+
+#define MAILBOX_LIST_INDEX_REFRESH_DELAY_MSECS 1000
+
+/* dovecot.list.index.log doesn't have to be kept for that long. */
+#define MAILBOX_LIST_INDEX_LOG_ROTATE_MIN_SIZE (8*1024)
+#define MAILBOX_LIST_INDEX_LOG_ROTATE_MAX_SIZE (64*1024)
+#define MAILBOX_LIST_INDEX_LOG_ROTATE_MIN_AGE_SECS (5*60)
+#define MAILBOX_LIST_INDEX_LOG2_MAX_AGE_SECS (10*60)
+
+static void mailbox_list_index_init_finish(struct mailbox_list *list);
+
+struct mailbox_list_index_module mailbox_list_index_module =
+	MODULE_CONTEXT_INIT(&mailbox_list_module_register);
+
+void mailbox_list_index_set_index_error(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	mailbox_list_set_internal_error(list);
+	mail_index_reset_error(ilist->index);
+}
+
+static void mailbox_list_index_init_pool(struct mailbox_list_index *ilist)
+{
+	ilist->mailbox_pool = pool_alloconly_create("mailbox list index", 4096);
+	hash_table_create_direct(&ilist->mailbox_names, ilist->mailbox_pool, 0);
+	hash_table_create_direct(&ilist->mailbox_hash, ilist->mailbox_pool, 0);
+}
+
+void mailbox_list_index_reset(struct mailbox_list_index *ilist)
+{
+	hash_table_destroy(&ilist->mailbox_names);
+	hash_table_destroy(&ilist->mailbox_hash);
+	pool_unref(&ilist->mailbox_pool);
+
+	ilist->mailbox_tree = NULL;
+	ilist->highest_name_id = 0;
+	ilist->sync_log_file_seq = 0;
+	ilist->sync_log_file_offset = 0;
+
+	mailbox_list_index_init_pool(ilist);
+}
+
+int mailbox_list_index_index_open(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	const struct mail_storage_settings *set = list->mail_set;
+	enum mail_index_open_flags index_flags;
+	unsigned int lock_timeout;
+
+	if (ilist->opened)
+		return 0;
+
+	if (mailbox_list_mkdir_missing_list_index_root(list) < 0)
+		return -1;
+
+	i_assert(ilist->index != NULL);
+
+	index_flags = mail_storage_settings_to_index_flags(set);
+	if (strcmp(list->name, MAILBOX_LIST_NAME_INDEX) == 0) {
+		/* LAYOUT=index. this is the only location for the mailbox
+		   data, so we must never move it into memory. */
+		index_flags |= MAIL_INDEX_OPEN_FLAG_NEVER_IN_MEMORY;
+	}
+	lock_timeout = set->mail_max_lock_timeout == 0 ? UINT_MAX :
+		set->mail_max_lock_timeout;
+
+	if (!mail_index_use_existing_permissions(ilist->index)) {
+		struct mailbox_permissions perm;
+
+		mailbox_list_get_root_permissions(list, &perm);
+		mail_index_set_permissions(ilist->index, perm.file_create_mode,
+					   perm.file_create_gid,
+					   perm.file_create_gid_origin);
+	}
+	const struct mail_index_optimization_settings optimize_set = {
+		.log = {
+			.min_size = MAILBOX_LIST_INDEX_LOG_ROTATE_MIN_SIZE,
+			.max_size = MAILBOX_LIST_INDEX_LOG_ROTATE_MAX_SIZE,
+			.min_age_secs = MAILBOX_LIST_INDEX_LOG_ROTATE_MIN_AGE_SECS,
+			.log2_max_age_secs = MAILBOX_LIST_INDEX_LOG2_MAX_AGE_SECS,
+		},
+	};
+	mail_index_set_optimization_settings(ilist->index, &optimize_set);
+
+	mail_index_set_fsync_mode(ilist->index, set->parsed_fsync_mode, 0);
+	mail_index_set_lock_method(ilist->index, set->parsed_lock_method,
+				   lock_timeout);
+	if (mail_index_open_or_create(ilist->index, index_flags) < 0) {
+		if (mail_index_move_to_memory(ilist->index) < 0) {
+			/* try opening once more. it should be created
+			   directly into memory now, except if it fails with
+			   LAYOUT=index backend. */
+			if (mail_index_open_or_create(ilist->index,
+						      index_flags) < 0) {
+				mailbox_list_set_internal_error(list);
+				return -1;
+			}
+		}
+	}
+	ilist->opened = TRUE;
+	return 0;
+}
+
+struct mailbox_list_index_node *
+mailbox_list_index_node_find_sibling(const struct mailbox_list *list,
+				     struct mailbox_list_index_node *node,
+				     const char *name)
+{
+	mailbox_list_name_unescape(&name, list->set.storage_name_escape_char);
+
+	while (node != NULL) {
+		if (strcmp(node->raw_name, name) == 0)
+			return node;
+		node = node->next;
+	}
+	return NULL;
+}
+
+static struct mailbox_list_index_node *
+mailbox_list_index_lookup_real(struct mailbox_list *list, const char *name)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_node *node = ilist->mailbox_tree;
+	const char *const *path;
+	unsigned int i;
+	char sep[2];
+
+	if (*name == '\0')
+		return mailbox_list_index_node_find_sibling(list, node, "");
+
+	sep[0] = mailbox_list_get_hierarchy_sep(list); sep[1] = '\0';
+	path = t_strsplit(name, sep);
+	for (i = 0;; i++) {
+		node = mailbox_list_index_node_find_sibling(list, node, path[i]);
+		if (node == NULL || path[i+1] == NULL)
+			break;
+		node = node->children;
+	}
+	return node;
+}
+
+struct mailbox_list_index_node *
+mailbox_list_index_lookup(struct mailbox_list *list, const char *name)
+{
+	struct mailbox_list_index_node *node;
+
+	T_BEGIN {
+		node = mailbox_list_index_lookup_real(list, name);
+	} T_END;
+	return node;
+}
+
+struct mailbox_list_index_node *
+mailbox_list_index_lookup_uid(struct mailbox_list_index *ilist, uint32_t uid)
+{
+	return hash_table_lookup(ilist->mailbox_hash, POINTER_CAST(uid));
+}
+
+void mailbox_list_index_node_get_path(const struct mailbox_list_index_node *node,
+				      char sep, string_t *str)
+{
+	if (node->parent != NULL) {
+		mailbox_list_index_node_get_path(node->parent, sep, str);
+		str_append_c(str, sep);
+	}
+	str_append(str, node->raw_name);
+}
+
+void mailbox_list_index_node_unlink(struct mailbox_list_index *ilist,
+				    struct mailbox_list_index_node *node)
+{
+	struct mailbox_list_index_node **prev;
+
+	prev = node->parent == NULL ?
+		&ilist->mailbox_tree : &node->parent->children;
+
+	while (*prev != node)
+		prev = &(*prev)->next;
+	*prev = node->next;
+}
+
+static int mailbox_list_index_parse_header(struct mailbox_list_index *ilist,
+					   struct mail_index_view *view)
+{
+	const void *data, *name_start, *p;
+	size_t i, len, size;
+	uint32_t id, prev_id = 0;
+	string_t *str;
+	char *name;
+	int ret = 0;
+
+	mail_index_map_get_header_ext(view, view->map, ilist->ext_id, &data, &size);
+	if (size == 0)
+		return 0;
+
+	str = t_str_new(128);
+	for (i = sizeof(struct mailbox_list_index_header); i < size; ) {
+		/* get id */
+		if (i + sizeof(id) > size)
+			return -1;
+		memcpy(&id, CONST_PTR_OFFSET(data, i), sizeof(id));
+		i += sizeof(id);
+
+		if (id <= prev_id) {
+			/* allow extra space in the end as long as last id=0 */
+			return id == 0 ? 0 : -1;
+		}
+		prev_id = id;
+
+		/* get name */
+		p = memchr(CONST_PTR_OFFSET(data, i), '\0', size-i);
+		if (p == NULL)
+			return -1;
+		name_start = CONST_PTR_OFFSET(data, i);
+		len = (const char *)p - (const char *)name_start;
+
+		if (uni_utf8_get_valid_data(name_start, len, str)) {
+			name = p_strndup(ilist->mailbox_pool, name_start, len);
+		} else {
+			/* corrupted index. fix the name. */
+			name = p_strdup(ilist->mailbox_pool, str_c(str));
+			str_truncate(str, 0);
+			ret = -1;
+		}
+
+		i += len + 1;
+
+		/* add id => name to hash table */
+		hash_table_insert(ilist->mailbox_names, POINTER_CAST(id), name);
+		ilist->highest_name_id = id;
+	}
+	i_assert(i == size);
+	return ret;
+}
+
+static void
+mailbox_list_index_generate_name(struct mailbox_list_index *ilist,
+				 struct mailbox_list_index_node *node,
+				 const char *prefix)
+{
+	guid_128_t guid;
+	char *name;
+
+	i_assert(node->name_id != 0);
+
+	guid_128_generate(guid);
+	name = p_strdup_printf(ilist->mailbox_pool, "%s%s", prefix,
+			       guid_128_to_string(guid));
+	node->raw_name = name;
+	node->flags |= MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME;
+
+	hash_table_insert(ilist->mailbox_names,
+			  POINTER_CAST(node->name_id), name);
+	if (ilist->highest_name_id < node->name_id)
+		ilist->highest_name_id = node->name_id;
+}
+
+static int mailbox_list_index_node_cmp(const struct mailbox_list_index_node *n1,
+				       const struct mailbox_list_index_node *n2)
+{
+	return  n1->parent == n2->parent &&
+		strcmp(n1->raw_name, n2->raw_name) == 0 ? 0 : -1;
+}
+
+static unsigned int
+mailbox_list_index_node_hash(const struct mailbox_list_index_node *node)
+{
+	return str_hash(node->raw_name) ^
+		POINTER_CAST_TO(node->parent, unsigned int);
+}
+
+static bool node_has_parent(const struct mailbox_list_index_node *parent,
+			    const struct mailbox_list_index_node *node)
+{
+	const struct mailbox_list_index_node *n;
+
+	for (n = parent; n != NULL; n = n->parent) {
+		if (n == node)
+			return TRUE;
+	}
+	return FALSE;
+}
+
+static int mailbox_list_index_parse_records(struct mailbox_list_index *ilist,
+					    struct mail_index_view *view,
+					    const char **error_r)
+{
+	struct mailbox_list_index_node *node, *parent;
+	HASH_TABLE(struct mailbox_list_index_node *,
+		   struct mailbox_list_index_node *) duplicate_hash;
+	const struct mail_index_record *rec;
+	const struct mailbox_list_index_record *irec;
+	const void *data;
+	bool expunged;
+	uint32_t seq, uid, count;
+	HASH_TABLE(uint8_t *, struct mailbox_list_index_node *) duplicate_guid;
+
+	*error_r = NULL;
+
+	pool_t dup_pool =
+		pool_alloconly_create(MEMPOOL_GROWING"duplicate pool", 2048);
+	hash_table_create(&duplicate_hash, dup_pool, 0,
+			  mailbox_list_index_node_hash,
+			  mailbox_list_index_node_cmp);
+	count = mail_index_view_get_messages_count(view);
+	if (!ilist->has_backing_store)
+		hash_table_create(&duplicate_guid, dup_pool, 0, guid_128_hash,
+				  guid_128_cmp);
+
+	for (seq = 1; seq <= count; seq++) {
+		node = p_new(ilist->mailbox_pool,
+			     struct mailbox_list_index_node, 1);
+		rec = mail_index_lookup(view, seq);
+		node->uid = rec->uid;
+		node->flags = rec->flags;
+
+		mail_index_lookup_ext(view, seq, ilist->ext_id,
+				      &data, &expunged);
+		if (data == NULL) {
+			*error_r = "Missing list extension data";
+			/* list index is missing, no point trying
+			   to do second scan either */
+			count = 0;
+			break;
+		}
+		irec = data;
+
+		node->name_id = irec->name_id;
+		if (node->name_id == 0) {
+			/* invalid name_id - assign a new one */
+			node->name_id = ++ilist->highest_name_id;
+			node->corrupted_ext = TRUE;
+		}
+		node->raw_name = hash_table_lookup(ilist->mailbox_names,
+					       POINTER_CAST(irec->name_id));
+		if (node->raw_name == NULL) {
+			*error_r = t_strdup_printf(
+				"name_id=%u not in index header", irec->name_id);
+			if (ilist->has_backing_store)
+				break;
+			/* generate a new name and use it */
+			mailbox_list_index_generate_name(ilist, node, "unknown-");
+		}
+
+		if (!ilist->has_backing_store && guid_128_is_empty(irec->guid) &&
+		    (rec->flags & (MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+				   MAILBOX_LIST_INDEX_FLAG_NOSELECT)) == 0) {
+			/* no backing store and mailbox has no GUID.
+			   it can't be selectable, but the flag is missing. */
+			node->flags |= MAILBOX_LIST_INDEX_FLAG_NOSELECT;
+			*error_r = t_strdup_printf(
+				"mailbox '%s' (uid=%u) is missing GUID - "
+				"marking it non-selectable", node->raw_name, node->uid);
+			node->corrupted_flags = TRUE;
+		}
+		if (!ilist->has_backing_store && !guid_128_is_empty(irec->guid) &&
+		    (rec->flags & (MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+				   MAILBOX_LIST_INDEX_FLAG_NOSELECT)) != 0) {
+			node->flags &= ENUM_NEGATE(MAILBOX_LIST_INDEX_FLAG_NONEXISTENT | MAILBOX_LIST_INDEX_FLAG_NOSELECT);
+			*error_r = t_strdup_printf(
+				"non-selectable mailbox '%s' (uid=%u) already has GUID - "
+				"marking it selectable", node->raw_name, node->uid);
+			node->corrupted_flags = TRUE;
+		}
+
+		if (!ilist->has_backing_store && !guid_128_is_empty(irec->guid)) {
+			struct mailbox_list_index_node *dup_node;
+			uint8_t *guid_p = p_memdup(dup_pool, irec->guid,
+						   sizeof(guid_128_t));
+			if ((dup_node = hash_table_lookup(duplicate_guid, guid_p)) != NULL) {
+				*error_r = t_strdup_printf(
+						"duplicate GUID %s for mailbox '%s' and '%s'",
+						guid_128_to_string(guid_p),
+						node->raw_name,
+						dup_node->raw_name);
+				node->corrupted_ext = TRUE;
+				ilist->corrupted_names_or_parents = TRUE;
+				ilist->call_corruption_callback = TRUE;
+			} else {
+				hash_table_insert(duplicate_guid, guid_p, node);
+			}
+		}
+
+		hash_table_insert(ilist->mailbox_hash,
+				  POINTER_CAST(node->uid), node);
+	}
+
+	/* do a second scan to create the actual mailbox tree hierarchy.
+	   this is needed because the parent_uid may be smaller or higher than
+	   the current node's uid */
+	if (*error_r != NULL && ilist->has_backing_store)
+		count = 0;
+	for (seq = 1; seq <= count; seq++) {
+		mail_index_lookup_uid(view, seq, &uid);
+		mail_index_lookup_ext(view, seq, ilist->ext_id,
+				      &data, &expunged);
+		irec = data;
+
+		node = mailbox_list_index_lookup_uid(ilist, uid);
+		i_assert(node != NULL);
+
+		if (irec->parent_uid != 0) {
+			/* node should have a parent */
+			parent = mailbox_list_index_lookup_uid(ilist,
+							       irec->parent_uid);
+			if (parent == NULL) {
+				*error_r = t_strdup_printf(
+					"parent_uid=%u points to nonexistent record",
+					irec->parent_uid);
+				if (ilist->has_backing_store)
+					break;
+				/* just place it under the root */
+				node->corrupted_ext = TRUE;
+			} else if (node_has_parent(parent, node)) {
+				*error_r = t_strdup_printf(
+					"parent_uid=%u loops to node itself (%s)",
+					uid, node->raw_name);
+				if (ilist->has_backing_store)
+					break;
+				/* just place it under the root */
+				node->corrupted_ext = TRUE;
+			} else {
+				node->parent = parent;
+				node->next = parent->children;
+				parent->children = node;
+			}
+		} else if (strcasecmp(node->raw_name, "INBOX") == 0) {
+			ilist->rebuild_on_missing_inbox = FALSE;
+		}
+		if (hash_table_lookup(duplicate_hash, node) == NULL)
+			hash_table_insert(duplicate_hash, node, node);
+		else {
+			const char *old_name = node->raw_name;
+
+			if (ilist->has_backing_store) {
+				*error_r = t_strdup_printf(
+					"Duplicate mailbox '%s' in index",
+					node->raw_name);
+				break;
+			}
+
+			/* we have only the mailbox list index and this node
+			   may have a different GUID, so rename it. */
+			node->corrupted_ext = TRUE;
+			node->name_id = ++ilist->highest_name_id;
+			mailbox_list_index_generate_name(ilist, node,
+				t_strconcat(node->raw_name, "-duplicate-", NULL));
+			*error_r = t_strdup_printf(
+				"Duplicate mailbox '%s' in index, renaming to %s",
+				old_name, node->raw_name);
+		}
+		if (node->parent == NULL) {
+			node->next = ilist->mailbox_tree;
+			ilist->mailbox_tree = node;
+		}
+	}
+	hash_table_destroy(&duplicate_hash);
+	if (!ilist->has_backing_store)
+		hash_table_destroy(&duplicate_guid);
+	pool_unref(&dup_pool);
+	return *error_r == NULL ? 0 : -1;
+}
+
+int mailbox_list_index_parse(struct mailbox_list *list,
+			     struct mail_index_view *view, bool force)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	const struct mail_index_header *hdr;
+	const char *error;
+
+	hdr = mail_index_get_header(view);
+	if (!force &&
+	    hdr->log_file_seq == ilist->sync_log_file_seq &&
+	    hdr->log_file_head_offset == ilist->sync_log_file_offset) {
+		/* nothing changed */
+		return 0;
+	}
+	if ((hdr->flags & MAIL_INDEX_HDR_FLAG_FSCKD) != 0) {
+		mailbox_list_set_critical(list,
+			"Mailbox list index was marked as fsck'd %s", ilist->path);
+		ilist->call_corruption_callback = TRUE;
+	}
+
+	mailbox_list_index_reset(ilist);
+	ilist->sync_log_file_seq = hdr->log_file_seq;
+	ilist->sync_log_file_offset = hdr->log_file_head_offset;
+
+	if (mailbox_list_index_parse_header(ilist, view) < 0) {
+		mailbox_list_set_critical(list,
+			"Corrupted mailbox list index header %s", ilist->path);
+		if (ilist->has_backing_store) {
+			mail_index_mark_corrupted(ilist->index);
+			return -1;
+		}
+		ilist->call_corruption_callback = TRUE;
+		ilist->corrupted_names_or_parents = TRUE;
+	}
+	if (mailbox_list_index_parse_records(ilist, view, &error) < 0) {
+		mailbox_list_set_critical(list,
+			"Corrupted mailbox list index %s: %s",
+			ilist->path, error);
+		if (ilist->has_backing_store) {
+			mail_index_mark_corrupted(ilist->index);
+			return -1;
+		}
+		ilist->call_corruption_callback = TRUE;
+		ilist->corrupted_names_or_parents = TRUE;
+	}
+	return 0;
+}
+
+const unsigned char *
+mailbox_name_hdr_encode(struct mailbox_list *list, const char *storage_name,
+			size_t *name_len_r)
+{
+	const char sep[] = {
+		mailbox_list_get_hierarchy_sep(list),
+		'\0'
+	};
+	const char **name_parts =
+		(const char **)p_strsplit(unsafe_data_stack_pool, storage_name, sep);
+	if (list->set.storage_name_escape_char != '\0') {
+		for (unsigned int i = 0; name_parts[i] != NULL; i++) {
+			mailbox_list_name_unescape(&name_parts[i],
+				list->set.storage_name_escape_char);
+		}
+	}
+
+	string_t *str = t_str_new(64);
+	str_append(str, name_parts[0]);
+	for (unsigned int i = 1; name_parts[i] != NULL; i++) {
+		str_append_c(str, '\0');
+		str_append(str, name_parts[i]);
+	}
+	*name_len_r = str_len(str);
+	return str_data(str);
+}
+
+const char *
+mailbox_name_hdr_decode_storage_name(struct mailbox_list *list,
+				     const unsigned char *name_hdr,
+				     size_t name_hdr_size)
+{
+	const char list_sep = mailbox_list_get_hierarchy_sep(list);
+	const char escape_char = list->set.storage_name_escape_char;
+	string_t *storage_name = t_str_new(name_hdr_size);
+	while (name_hdr_size > 0) {
+		const unsigned char *p = memchr(name_hdr, '\0', name_hdr_size);
+		size_t name_part_len;
+		if (p == NULL) {
+			name_part_len = name_hdr_size;
+			name_hdr_size = 0;
+		} else {
+			name_part_len = p - name_hdr;
+			i_assert(name_hdr_size > name_part_len);
+			name_hdr_size -= name_part_len + 1;
+		}
+
+		if (escape_char == '\0')
+			str_append_data(storage_name, name_hdr, name_part_len);
+		else {
+			const char *name_part =
+				t_strndup(name_hdr, name_part_len);
+			str_append(storage_name,
+				   mailbox_list_escape_name_params(name_part,
+					"", '\0', list_sep, escape_char,
+					list->set.maildir_name));
+		}
+
+		if (p != NULL) {
+			name_hdr += name_part_len + 1;
+			str_append_c(storage_name, list_sep);
+		}
+	}
+	return str_c(storage_name);
+}
+
+bool mailbox_list_index_need_refresh(struct mailbox_list_index *ilist,
+				     struct mail_index_view *view)
+{
+	const struct mailbox_list_index_header *hdr;
+	const void *data;
+	size_t size;
+
+	if (!ilist->has_backing_store)
+		return FALSE;
+
+	mail_index_get_header_ext(view, ilist->ext_id, &data, &size);
+	hdr = data;
+	return hdr != NULL && hdr->refresh_flag != 0;
+}
+
+int mailbox_list_index_refresh(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	if (ilist->syncing)
+		return 0;
+	if (ilist->last_refresh_timeval.tv_usec == ioloop_timeval.tv_usec &&
+	    ilist->last_refresh_timeval.tv_sec == ioloop_timeval.tv_sec) {
+		/* we haven't been to ioloop since last refresh, skip checking
+		   it. when we're accessing many mailboxes at once (e.g.
+		   opening a virtual mailbox) we don't want to stat/read the
+		   index every single time. */
+		return 0;
+	}
+
+	return mailbox_list_index_refresh_force(list);
+}
+
+int mailbox_list_index_refresh_force(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mail_index_view *view;
+	int ret;
+	bool refresh;
+
+	i_assert(!ilist->syncing);
+
+	ilist->last_refresh_timeval = ioloop_timeval;
+	if (mailbox_list_index_index_open(list) < 0)
+		return -1;
+	if (mail_index_refresh(ilist->index) < 0) {
+		mailbox_list_index_set_index_error(list);
+		return -1;
+	}
+
+	view = mail_index_view_open(ilist->index);
+	if ((refresh = mailbox_list_index_need_refresh(ilist, view)) ||
+	    ilist->mailbox_tree == NULL) {
+		/* refresh list of mailboxes */
+		ret = mailbox_list_index_sync(list, refresh);
+	} else {
+		ret = mailbox_list_index_parse(list, view, FALSE);
+	}
+	mail_index_view_close(&view);
+
+	if (mailbox_list_index_handle_corruption(list) < 0) {
+		const char *errstr;
+		enum mail_error error;
+
+		errstr = mailbox_list_get_last_internal_error(list, &error);
+		mailbox_list_set_error(list, error, t_strdup_printf(
+			"Failed to rebuild mailbox list index: %s", errstr));
+		ret = -1;
+	}
+	return ret;
+}
+
+static void mailbox_list_index_refresh_timeout(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	timeout_remove(&ilist->to_refresh);
+	(void)mailbox_list_index_refresh(list);
+}
+
+void mailbox_list_index_refresh_later(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_header new_hdr;
+	struct mail_index_view *view;
+	struct mail_index_transaction *trans;
+
+	memset(&ilist->last_refresh_timeval, 0,
+	       sizeof(ilist->last_refresh_timeval));
+
+	if (!ilist->has_backing_store)
+		return;
+
+	(void)mailbox_list_index_index_open(list);
+
+	view = mail_index_view_open(ilist->index);
+	if (!mailbox_list_index_need_refresh(ilist, view)) {
+		new_hdr.refresh_flag = 1;
+
+		trans = mail_index_transaction_begin(view,
+					MAIL_INDEX_TRANSACTION_FLAG_EXTERNAL);
+		mail_index_update_header_ext(trans, ilist->ext_id,
+			offsetof(struct mailbox_list_index_header, refresh_flag),
+			&new_hdr.refresh_flag, sizeof(new_hdr.refresh_flag));
+		if (mail_index_transaction_commit(&trans) < 0)
+			mail_index_mark_corrupted(ilist->index);
+
+	}
+	mail_index_view_close(&view);
+
+	if (ilist->to_refresh == NULL) {
+		ilist->to_refresh =
+			timeout_add(MAILBOX_LIST_INDEX_REFRESH_DELAY_MSECS,
+				    mailbox_list_index_refresh_timeout, list);
+	}
+}
+
+static int
+list_handle_corruption_locked(struct mailbox_list *list,
+			      enum mail_storage_list_index_rebuild_reason reason)
+{
+	struct mail_storage *storage;
+	const char *errstr;
+	enum mail_error error;
+
+	array_foreach_elem(&list->ns->all_storages, storage) {
+		if (storage->v.list_index_rebuild == NULL)
+			continue;
+
+		if (storage->v.list_index_rebuild(storage, reason) < 0) {
+			errstr = mail_storage_get_last_internal_error(storage, &error);
+			mailbox_list_set_error(list, error, errstr);
+			return -1;
+		} else {
+			/* FIXME: implement a generic handler that
+			   just lists mailbox directories in filesystem
+			   and adds the missing ones to the index. */
+		}
+	}
+	return mailbox_list_index_set_uncorrupted(list);
+}
+
+int mailbox_list_index_handle_corruption(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	enum mail_storage_list_index_rebuild_reason reason;
+	int ret;
+
+	if (ilist->call_corruption_callback)
+		reason = MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_CORRUPTED;
+	else if (ilist->rebuild_on_missing_inbox)
+		reason = MAIL_STORAGE_LIST_INDEX_REBUILD_REASON_NO_INBOX;
+	else
+		return 0;
+
+	if (list->disable_rebuild_on_corruption)
+		return 0;
+
+	/* make sure we don't recurse */
+	if (ilist->handling_corruption)
+		return 0;
+	ilist->handling_corruption = TRUE;
+
+	/* Perform the rebuilding locked. Note that if we're here because
+	   INBOX wasn't found, this may be because another process is in the
+	   middle of creating it. Waiting for the lock here makes sure that
+	   we don't start rebuilding before it's finished. In that case the
+	   rebuild is a bit unnecessary, but harmless (and avoiding the rebuild
+	   just adds extra code complexity). */
+	if (mailbox_list_lock(list) < 0)
+		ret = -1;
+	else {
+		ret = list_handle_corruption_locked(list, reason);
+		mailbox_list_unlock(list);
+	}
+	ilist->handling_corruption = FALSE;
+	return ret;
+}
+
+int mailbox_list_index_set_uncorrupted(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_sync_context *sync_ctx;
+
+	ilist->call_corruption_callback = FALSE;
+	ilist->rebuild_on_missing_inbox = FALSE;
+
+	if (mailbox_list_index_sync_begin(list, &sync_ctx) < 0)
+		return -1;
+
+	mail_index_unset_fscked(sync_ctx->trans);
+	return mailbox_list_index_sync_end(&sync_ctx, TRUE);
+}
+
+bool mailbox_list_index_get_index(struct mailbox_list *list,
+				  struct mail_index **index_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(list);
+
+	if (ilist == NULL)
+		return FALSE;
+	*index_r = ilist->index;
+	return TRUE;
+}
+
+int mailbox_list_index_view_open(struct mailbox *box, bool require_refreshed,
+				 struct mail_index_view **view_r,
+				 uint32_t *seq_r)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(box->list);
+	struct mailbox_list_index_node *node;
+	struct mail_index_view *view;
+	const char *reason = NULL;
+	uint32_t seq;
+	int ret;
+
+	if (ilist == NULL) {
+		/* mailbox list indexes aren't enabled */
+		return 0;
+	}
+	if (MAILBOX_IS_NEVER_IN_INDEX(box) && require_refreshed) {
+		/* Optimization: Caller wants the list index to be up-to-date
+		   for this mailbox, but this mailbox isn't updated to the list
+		   index at all. */
+		return 0;
+	}
+	if (mailbox_list_index_refresh(box->list) < 0) {
+		mail_storage_copy_list_error(box->storage, box->list);
+		return -1;
+	}
+
+	node = mailbox_list_index_lookup(box->list, box->name);
+	if (node == NULL) {
+		/* mailbox not found */
+		e_debug(box->event, "Couldn't open mailbox in list index: "
+			"Mailbox not found");
+		return 0;
+	}
+
+	view = mail_index_view_open(ilist->index);
+	if (mailbox_list_index_need_refresh(ilist, view)) {
+		/* mailbox_list_index_refresh_later() was called.
+		   Can't trust the index's contents. */
+		reason = "Refresh-flag set";
+		ret = 1;
+	} else if (!mail_index_lookup_seq(view, node->uid, &seq)) {
+		/* our in-memory tree is out of sync */
+		ret = 1;
+		reason = "Mailbox no longer exists in index";
+	} else if (!require_refreshed) {
+		/* this operation doesn't need the index to be up-to-date */
+		ret = 0;
+	} else {
+		ret = box->v.list_index_has_changed == NULL ? 0 :
+			box->v.list_index_has_changed(box, view, seq, FALSE,
+						      &reason);
+		i_assert(ret <= 0 || reason != NULL);
+	}
+
+	if (ret != 0) {
+		/* error / mailbox has changed. we'll need to sync it. */
+		if (ret < 0)
+			mailbox_list_index_refresh_later(box->list);
+		else {
+			i_assert(reason != NULL);
+			e_debug(box->event,
+				"Couldn't open mailbox in list index: %s",
+				reason);
+			ilist->index_last_check_changed = TRUE;
+		}
+		mail_index_view_close(&view);
+		return ret < 0 ? -1 : 0;
+	}
+
+	*view_r = view;
+	*seq_r = seq;
+	return 1;
+}
+
+static void mailbox_list_index_deinit(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	timeout_remove(&ilist->to_refresh);
+	if (ilist->index != NULL) {
+		hash_table_destroy(&ilist->mailbox_hash);
+		hash_table_destroy(&ilist->mailbox_names);
+		pool_unref(&ilist->mailbox_pool);
+		if (ilist->opened)
+			mail_index_close(ilist->index);
+		mail_index_free(&ilist->index);
+	}
+	ilist->module_ctx.super.deinit(list);
+}
+
+static void
+mailbox_list_index_refresh_if_found(struct mailbox_list *list,
+				    const char *name, bool selectable)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+	struct mailbox_list_index_node *node;
+
+	if (ilist->syncing)
+		return;
+
+	mailbox_list_last_error_push(list);
+	(void)mailbox_list_index_refresh_force(list);
+	node = mailbox_list_index_lookup(list, name);
+	if (node != NULL &&
+	    (!selectable ||
+	     (node->flags & (MAILBOX_LIST_INDEX_FLAG_NONEXISTENT |
+			     MAILBOX_LIST_INDEX_FLAG_NOSELECT)) == 0)) {
+		/* index is out of sync - refresh */
+		mailbox_list_index_refresh_later(list);
+	}
+	mailbox_list_last_error_pop(list);
+}
+
+static void mailbox_list_index_refresh_if_not_found(struct mailbox_list *list,
+						    const char *name)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	if (ilist->syncing)
+		return;
+
+	mailbox_list_last_error_push(list);
+	(void)mailbox_list_index_refresh_force(list);
+	if (mailbox_list_index_lookup(list, name) == NULL) {
+		/* index is out of sync - refresh */
+		mailbox_list_index_refresh_later(list);
+	}
+	mailbox_list_last_error_pop(list);
+}
+
+static int mailbox_list_index_open_mailbox(struct mailbox *box)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if (ibox->module_ctx.super.open(box) < 0) {
+		if (mailbox_get_last_mail_error(box) == MAIL_ERROR_NOTFOUND)
+			mailbox_list_index_refresh_if_found(box->list, box->name, TRUE);
+		return -1;
+	}
+	return 0;
+}
+
+static int
+mailbox_list_index_create_mailbox(struct mailbox *box,
+				  const struct mailbox_update *update,
+				  bool directory)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if (ibox->module_ctx.super.create_box(box, update, directory) < 0) {
+		if (mailbox_get_last_mail_error(box) == MAIL_ERROR_EXISTS)
+			mailbox_list_index_refresh_if_not_found(box->list, box->name);
+		return -1;
+	}
+	mailbox_list_index_refresh_later(box->list);
+	return 0;
+}
+
+static int
+mailbox_list_index_update_mailbox(struct mailbox *box,
+				  const struct mailbox_update *update)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	if (ibox->module_ctx.super.update_box(box, update) < 0) {
+		if (mailbox_get_last_mail_error(box) == MAIL_ERROR_NOTFOUND)
+			mailbox_list_index_refresh_if_found(box->list, box->name, TRUE);
+		return -1;
+	}
+
+	mailbox_list_index_update_mailbox_index(box, update);
+	return 0;
+}
+
+static int
+mailbox_list_index_delete_mailbox(struct mailbox_list *list, const char *name)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	if (ilist->module_ctx.super.delete_mailbox(list, name) < 0) {
+		if (mailbox_list_get_last_mail_error(list) == MAIL_ERROR_NOTFOUND)
+			mailbox_list_index_refresh_if_found(list, name, FALSE);
+		return -1;
+	}
+	mailbox_list_index_refresh_later(list);
+	return 0;
+}
+
+static int
+mailbox_list_index_delete_dir(struct mailbox_list *list, const char *name)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(list);
+
+	if (ilist->module_ctx.super.delete_dir(list, name) < 0) {
+		if (mailbox_list_get_last_mail_error(list) == MAIL_ERROR_NOTFOUND)
+			mailbox_list_index_refresh_if_found(list, name, FALSE);
+		return -1;
+	}
+	mailbox_list_index_refresh_later(list);
+	return 0;
+}
+
+static int
+mailbox_list_index_rename_mailbox(struct mailbox_list *oldlist,
+				  const char *oldname,
+				  struct mailbox_list *newlist,
+				  const char *newname)
+{
+	struct mailbox_list_index *oldilist = INDEX_LIST_CONTEXT_REQUIRE(oldlist);
+
+	if (oldilist->module_ctx.super.rename_mailbox(oldlist, oldname,
+						      newlist, newname) < 0) {
+		if (mailbox_list_get_last_mail_error(oldlist) == MAIL_ERROR_NOTFOUND)
+			mailbox_list_index_refresh_if_found(oldlist, oldname, FALSE);
+		if (mailbox_list_get_last_mail_error(newlist) == MAIL_ERROR_EXISTS)
+			mailbox_list_index_refresh_if_not_found(newlist, newname);
+		return -1;
+	}
+	mailbox_list_index_refresh_later(oldlist);
+	if (oldlist != newlist)
+		mailbox_list_index_refresh_later(newlist);
+	return 0;
+}
+
+static int
+mailbox_list_index_set_subscribed(struct mailbox_list *_list,
+				  const char *name, bool set)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(_list);
+	struct mail_index_view *view;
+	struct mail_index_transaction *trans;
+	const void *data;
+	size_t size;
+	uint32_t counter;
+
+	if (ilist->module_ctx.super.set_subscribed(_list, name, set) < 0)
+		return -1;
+
+	/* update the "subscriptions changed" counter/timestamp. its purpose
+	   is to trigger NOTIFY watcher to handle SubscriptionChange events */
+	if (mailbox_list_index_index_open(_list) < 0)
+		return -1;
+	view = mail_index_view_open(ilist->index);
+	mail_index_get_header_ext(view, ilist->subs_hdr_ext_id, &data, &size);
+	if (size != sizeof(counter))
+		counter = ioloop_time;
+	else {
+		memcpy(&counter, data, size);
+		if (++counter < (uint32_t)ioloop_time)
+			counter = ioloop_time;
+	}
+
+	trans = mail_index_transaction_begin(view,
+					MAIL_INDEX_TRANSACTION_FLAG_EXTERNAL);
+	mail_index_update_header_ext(trans, ilist->subs_hdr_ext_id,
+				     0, &counter, sizeof(counter));
+	(void)mail_index_transaction_commit(&trans);
+	mail_index_view_close(&view);
+	return 0;
+}
+
+static bool mailbox_list_index_is_enabled(struct mailbox_list *list)
+{
+	if (!list->mail_set->mailbox_list_index ||
+	    (list->props & MAILBOX_LIST_PROP_NO_LIST_INDEX) != 0)
+		return FALSE;
+
+	i_assert(list->set.list_index_fname != NULL);
+	if (list->set.list_index_fname[0] == '\0')
+		return FALSE;
+	return TRUE;
+}
+
+static void mailbox_list_index_created(struct mailbox_list *list)
+{
+	struct mailbox_list_vfuncs *v = list->vlast;
+	struct mailbox_list_index *ilist;
+	bool has_backing_store;
+
+	/* layout=index doesn't have any backing store */
+	has_backing_store = strcmp(list->name, MAILBOX_LIST_NAME_INDEX) != 0;
+
+	if (!mailbox_list_index_is_enabled(list)) {
+		/* reserve the module context anyway, so syncing code knows
+		   that the index is disabled */
+		i_assert(has_backing_store);
+		ilist = NULL;
+		MODULE_CONTEXT_SET(list, mailbox_list_index_module, ilist);
+		return;
+	}
+
+	ilist = p_new(list->pool, struct mailbox_list_index, 1);
+	ilist->module_ctx.super = *v;
+	list->vlast = &ilist->module_ctx.super;
+	ilist->has_backing_store = has_backing_store;
+	ilist->pending_init = TRUE;
+
+	v->deinit = mailbox_list_index_deinit;
+	v->iter_init = mailbox_list_index_iter_init;
+	v->iter_deinit = mailbox_list_index_iter_deinit;
+	v->iter_next = mailbox_list_index_iter_next;
+
+	v->delete_mailbox = mailbox_list_index_delete_mailbox;
+	v->delete_dir = mailbox_list_index_delete_dir;
+	v->rename_mailbox = mailbox_list_index_rename_mailbox;
+	v->set_subscribed = mailbox_list_index_set_subscribed;
+
+	v->notify_init = mailbox_list_index_notify_init;
+	v->notify_next = mailbox_list_index_notify_next;
+	v->notify_deinit = mailbox_list_index_notify_deinit;
+	v->notify_wait = mailbox_list_index_notify_wait;
+	v->notify_flush = mailbox_list_index_notify_flush;
+
+	MODULE_CONTEXT_SET(list, mailbox_list_index_module, ilist);
+
+	if ((list->flags & MAILBOX_LIST_FLAG_SECONDARY) != 0) {
+		/* secondary lists aren't accessible via namespaces, so we
+		   need to finish them now. */
+		mailbox_list_index_init_finish(list);
+	}
+}
+
+static void mailbox_list_index_init_finish(struct mailbox_list *list)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(list);
+	const char *dir;
+
+	if (ilist == NULL || !ilist->pending_init)
+		return;
+	ilist->pending_init = FALSE;
+
+	/* we've delayed this part of the initialization so that mbox format
+	   can override the index root directory path */
+	if (!mailbox_list_get_root_path(list, MAILBOX_LIST_PATH_TYPE_LIST_INDEX,
+					&dir)) {
+		/* in-memory indexes */
+		dir = NULL;
+	}
+	i_assert(ilist->has_backing_store || dir != NULL);
+
+	i_assert(list->set.list_index_fname != NULL);
+	ilist->path = dir == NULL ? "(in-memory mailbox list index)" :
+		p_strdup_printf(list->pool, "%s/%s", dir, list->set.list_index_fname);
+	ilist->index = mail_index_alloc(list->ns->user->event,
+					dir, list->set.list_index_fname);
+	ilist->rebuild_on_missing_inbox = !ilist->has_backing_store &&
+		(list->ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0;
+
+	ilist->ext_id = mail_index_ext_register(ilist->index, "list",
+				sizeof(struct mailbox_list_index_header),
+				sizeof(struct mailbox_list_index_record),
+				sizeof(uint32_t));
+	ilist->subs_hdr_ext_id = mail_index_ext_register(ilist->index, "subs",
+							 sizeof(uint32_t), 0,
+							 sizeof(uint32_t));
+	mailbox_list_index_init_pool(ilist);
+
+	mailbox_list_index_status_init_finish(list);
+}
+
+static void
+mailbox_list_index_namespaces_added(struct mail_namespace *namespaces)
+{
+	struct mail_namespace *ns;
+
+	for (ns = namespaces; ns != NULL; ns = ns->next)
+		mailbox_list_index_init_finish(ns->list);
+}
+
+static struct mailbox_sync_context *
+mailbox_list_index_sync_init(struct mailbox *box,
+			     enum mailbox_sync_flags flags)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(box);
+
+	mailbox_list_index_status_sync_init(box);
+	if (!ibox->have_backend)
+		mailbox_list_index_backend_sync_init(box, flags);
+	return ibox->module_ctx.super.sync_init(box, flags);
+}
+
+static int
+mailbox_list_index_sync_deinit(struct mailbox_sync_context *ctx,
+			       struct mailbox_sync_status *status_r)
+{
+	struct index_list_mailbox *ibox = INDEX_LIST_STORAGE_CONTEXT(ctx->box);
+	struct mailbox *box = ctx->box;
+
+	if (ibox->module_ctx.super.sync_deinit(ctx, status_r) < 0)
+		return -1;
+	ctx = NULL;
+
+	mailbox_list_index_status_sync_deinit(box);
+	if (ibox->have_backend)
+		return mailbox_list_index_backend_sync_deinit(box);
+	else
+		return 0;
+}
+
+static void mailbox_list_index_mailbox_allocated(struct mailbox *box)
+{
+	struct mailbox_vfuncs *v = box->vlast;
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(box->list);
+	struct index_list_mailbox *ibox;
+
+	if (ilist == NULL)
+		return;
+
+	ibox = p_new(box->pool, struct index_list_mailbox, 1);
+	ibox->module_ctx.super = *v;
+	box->vlast = &ibox->module_ctx.super;
+	MODULE_CONTEXT_SET(box, index_list_storage_module, ibox);
+
+	/* for layout=index these get overridden */
+	v->open = mailbox_list_index_open_mailbox;
+	v->create_box = mailbox_list_index_create_mailbox;
+	v->update_box = mailbox_list_index_update_mailbox;
+
+	/* These are used by both status and backend code, but they can't both
+	   be overriding the same function pointer since they share the
+	   super pointer. */
+	v->sync_init = mailbox_list_index_sync_init;
+	v->sync_deinit = mailbox_list_index_sync_deinit;
+
+	mailbox_list_index_status_init_mailbox(v);
+	ibox->have_backend = mailbox_list_index_backend_init_mailbox(box, v);
+}
+
+static struct mail_storage_hooks mailbox_list_index_hooks = {
+	.mailbox_list_created = mailbox_list_index_created,
+	.mail_namespaces_added = mailbox_list_index_namespaces_added,
+	.mailbox_allocated = mailbox_list_index_mailbox_allocated
+};
+
+void mailbox_list_index_init(void); /* called in mailbox-list-register.c */
+
+void mailbox_list_index_init(void)
+{
+	mail_storage_hooks_add_internal(&mailbox_list_index_hooks);
+}
diff --git a/src/lib-storage/list/mailbox-list-index.h b/src/lib-storage/list/mailbox-list-index.h
new file mode 100644
index 0000000..0109f5d
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-index.h
@@ -0,0 +1,250 @@
+#ifndef MAILBOX_LIST_INDEX_H
+#define MAILBOX_LIST_INDEX_H
+
+/* Mailbox list index basically contains:
+
+   Header contains ID => name mapping. The name isn't the full mailbox name,
+   but rather each hierarchy level has its own ID and name. For example a
+   mailbox name "foo/bar" (with '/' as separator) would have separate IDs for
+   "foo" and "bar" names.
+
+   The records contain { parent_uid, uid, name_id } field that can be used to
+   build the whole mailbox tree. parent_uid=0 means root, otherwise it's the
+   parent node's uid.
+
+   Each record also contains GUID for each selectable mailbox. If a mailbox
+   is recreated using the same name, its GUID also changes. Note however that
+   the UID doesn't change, because the UID refers to the mailbox name, not to
+   the mailbox itself.
+
+   The records may contain also extensions for allowing mailbox_get_status()
+   to return values directly from the mailbox list index. Storage backends
+   may also add their own extensions to figure out if a record is up to date.
+*/
+
+#include "module-context.h"
+#include "mail-types.h"
+#include "mail-storage.h"
+#include "mailbox-list-private.h"
+
+#include <sys/time.h>
+
+#define MAILBOX_LIST_INDEX_HIERARCHY_SEP '~'
+#define MAILBOX_LIST_INDEX_HIERARCHY_ALT_SEP '^'
+
+#define INDEX_LIST_CONTEXT(obj) \
+	MODULE_CONTEXT(obj, mailbox_list_index_module)
+#define INDEX_LIST_CONTEXT_REQUIRE(obj) \
+	MODULE_CONTEXT_REQUIRE(obj, mailbox_list_index_module)
+
+/* Should the STATUS information for this mailbox not be written to the
+   mailbox list index? */
+#define MAILBOX_IS_NEVER_IN_INDEX(box) \
+	((box)->inbox_any && !(box)->storage->set->mailbox_list_index_include_inbox)
+
+struct mail_index_view;
+struct mailbox_index_vsize;
+struct mailbox_vfuncs;
+
+/* stored in mail_index_record.flags: */
+enum mailbox_list_index_flags {
+	MAILBOX_LIST_INDEX_FLAG_NONEXISTENT = MAIL_DELETED,
+	MAILBOX_LIST_INDEX_FLAG_NOSELECT = MAIL_DRAFT,
+	MAILBOX_LIST_INDEX_FLAG_NOINFERIORS = MAIL_ANSWERED,
+	MAILBOX_LIST_INDEX_FLAG_CORRUPTED_NAME = MAIL_SEEN,
+
+	/* set during syncing for mailboxes that still exist */
+	MAILBOX_LIST_INDEX_FLAG_SYNC_EXISTS = MAIL_FLAGGED
+};
+
+struct mailbox_list_index_header {
+	uint8_t refresh_flag;
+	/* array of { uint32_t id; char name[]; } */
+};
+
+struct mailbox_list_index_record {
+	/* points to given id in header */
+	uint32_t name_id;
+	/* parent mailbox's UID, 0 = root */
+	uint32_t parent_uid;
+
+	/* the following fields are temporarily zero while unknown,
+	   also permanently zero for \NoSelect and \Nonexistent mailboxes: */
+
+	guid_128_t guid;
+	uint32_t uid_validity;
+};
+
+struct mailbox_list_index_msgs_record {
+	uint32_t messages;
+	uint32_t unseen;
+	uint32_t recent;
+	uint32_t uidnext;
+};
+
+struct mailbox_list_index_node {
+	struct mailbox_list_index_node *parent;
+	struct mailbox_list_index_node *next;
+	struct mailbox_list_index_node *children;
+
+	uint32_t name_id, uid;
+	enum mailbox_list_index_flags flags;
+	/* extension data is corrupted on disk - need to update it */
+	bool corrupted_ext;
+	/* flags are corrupted on disk - need to update it */
+	bool corrupted_flags;
+	const char *raw_name;
+};
+
+struct mailbox_list_index {
+	union mailbox_list_module_context module_ctx;
+
+	const char *path;
+	struct mail_index *index;
+	uint32_t ext_id, msgs_ext_id, hmodseq_ext_id, subs_hdr_ext_id;
+	uint32_t vsize_ext_id, first_saved_ext_id;
+	struct timeval last_refresh_timeval;
+
+	pool_t mailbox_pool;
+	/* uin32_t id => name */
+	HASH_TABLE(void *, char *) mailbox_names;
+	uint32_t highest_name_id;
+
+	struct mailbox_list_index_sync_context *sync_ctx;
+	uint32_t sync_log_file_seq;
+	uoff_t sync_log_file_offset;
+	uint32_t sync_stamp;
+	struct timeout *to_refresh;
+
+	/* uint32_t uid => node */
+	HASH_TABLE(void *, struct mailbox_list_index_node *) mailbox_hash;
+	struct mailbox_list_index_node *mailbox_tree;
+
+	bool pending_init:1;
+	bool opened:1;
+	bool syncing:1;
+	bool updating_status:1;
+	bool has_backing_store:1;
+	bool index_last_check_changed:1;
+	bool corrupted_names_or_parents:1;
+	bool handling_corruption:1;
+	bool call_corruption_callback:1;
+	bool rebuild_on_missing_inbox:1;
+	bool force_resynced:1;
+	bool force_resync_failed:1;
+};
+
+struct mailbox_list_index_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+	pool_t mailbox_pool;
+
+	struct mailbox_info info;
+	pool_t info_pool;
+
+	size_t parent_len;
+	string_t *path;
+	struct mailbox_list_index_node *next_node;
+
+	bool failed:1;
+	bool prefix_inbox_list:1;
+};
+
+extern MODULE_CONTEXT_DEFINE(mailbox_list_index_module,
+			     &mailbox_list_module_register);
+
+void mailbox_list_index_set_index_error(struct mailbox_list *list);
+struct mailbox_list_index_node *
+mailbox_list_index_lookup(struct mailbox_list *list, const char *name);
+struct mailbox_list_index_node *
+mailbox_list_index_lookup_uid(struct mailbox_list_index *ilist, uint32_t uid);
+void mailbox_list_index_node_get_path(const struct mailbox_list_index_node *node,
+				      char sep, string_t *str);
+void mailbox_list_index_node_unlink(struct mailbox_list_index *ilist,
+				    struct mailbox_list_index_node *node);
+
+/* Return mailbox name encoded into box-name header. */
+const unsigned char *
+mailbox_name_hdr_encode(struct mailbox_list *list, const char *storage_name,
+			size_t *name_len_r);
+/* Return mailbox name decoded from box-name header. */
+const char *
+mailbox_name_hdr_decode_storage_name(struct mailbox_list *list,
+				     const unsigned char *name_hdr,
+				     size_t name_hdr_size);
+
+int mailbox_list_index_index_open(struct mailbox_list *list);
+bool mailbox_list_index_need_refresh(struct mailbox_list_index *ilist,
+				     struct mail_index_view *view);
+/* Refresh the index, but only if it hasn't been refreshed "recently"
+   (= within this same ioloop run) */
+int mailbox_list_index_refresh(struct mailbox_list *list);
+/* Refresh the index regardless of when the last refresh was done. */
+int mailbox_list_index_refresh_force(struct mailbox_list *list);
+void mailbox_list_index_refresh_later(struct mailbox_list *list);
+int mailbox_list_index_handle_corruption(struct mailbox_list *list);
+int mailbox_list_index_set_uncorrupted(struct mailbox_list *list);
+
+/* Returns TRUE and index_r if mailbox list index exists, FALSE if not. */
+bool mailbox_list_index_get_index(struct mailbox_list *list,
+				  struct mail_index **index_r);
+/* Open mailbox list index's view and get the given mailbox's sequence number
+   in it. If require_refreshed is TRUE, the mailbox must have up-to-date
+   information in the mailbox list index. Returns 1 if ok, 0 if mailbox wasn't
+   found or it wasn't up-to-date as requested, -1 if there was an error. The
+   error is stored to the mailbox storage. */
+int mailbox_list_index_view_open(struct mailbox *box, bool require_refreshed,
+				 struct mail_index_view **view_r,
+				 uint32_t *seq_r);
+
+struct mailbox_list_index_node *
+mailbox_list_index_node_find_sibling(const struct mailbox_list *list,
+				     struct mailbox_list_index_node *node,
+				     const char *name);
+void mailbox_list_index_reset(struct mailbox_list_index *ilist);
+int mailbox_list_index_parse(struct mailbox_list *list,
+			     struct mail_index_view *view, bool force);
+
+struct mailbox_list_iterate_context *
+mailbox_list_index_iter_init(struct mailbox_list *list,
+			     const char *const *patterns,
+			     enum mailbox_list_iter_flags flags);
+const struct mailbox_info *
+mailbox_list_index_iter_next(struct mailbox_list_iterate_context *ctx);
+int mailbox_list_index_iter_deinit(struct mailbox_list_iterate_context *ctx);
+
+bool mailbox_list_index_status(struct mailbox_list *list,
+			       struct mail_index_view *view,
+			       uint32_t seq, enum mailbox_status_items items,
+			       struct mailbox_status *status_r,
+			       uint8_t *mailbox_guid,
+			       struct mailbox_index_vsize *vsize_r,
+			       const char **reason_r);
+void mailbox_list_index_status_set_info_flags(struct mailbox *box, uint32_t uid,
+					      enum mailbox_info_flags *flags);
+void mailbox_list_index_update_mailbox_index(struct mailbox *box,
+					     const struct mailbox_update *update);
+
+int mailbox_list_index_notify_init(struct mailbox_list *list,
+				   enum mailbox_list_notify_event mask,
+				   struct mailbox_list_notify **notify_r);
+void mailbox_list_index_notify_deinit(struct mailbox_list_notify *notify);
+int mailbox_list_index_notify_next(struct mailbox_list_notify *notify,
+				   const struct mailbox_list_notify_rec **rec_r);
+void mailbox_list_index_notify_wait(struct mailbox_list_notify *notify,
+				    void (*callback)(void *context),
+				    void *context);
+void mailbox_list_index_notify_flush(struct mailbox_list_notify *notify);
+
+void mailbox_list_index_status_init_mailbox(struct mailbox_vfuncs *v);
+bool mailbox_list_index_backend_init_mailbox(struct mailbox *box,
+					     struct mailbox_vfuncs *v);
+void mailbox_list_index_status_init_finish(struct mailbox_list *list);
+
+void mailbox_list_index_status_sync_init(struct mailbox *box);
+void mailbox_list_index_status_sync_deinit(struct mailbox *box);
+
+void mailbox_list_index_backend_sync_init(struct mailbox *box,
+					  enum mailbox_sync_flags flags);
+int mailbox_list_index_backend_sync_deinit(struct mailbox *box);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-iter-private.h b/src/lib-storage/list/mailbox-list-iter-private.h
new file mode 100644
index 0000000..47de2ce
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-iter-private.h
@@ -0,0 +1,42 @@
+#ifndef MAILBOX_LIST_ITER_PRIVATE_H
+#define MAILBOX_LIST_ITER_PRIVATE_H
+
+#include "mailbox-list-private.h"
+#include "mailbox-list-iter.h"
+#include "mailbox-list-delete.h"
+
+struct autocreate_box {
+	const char *name;
+	const struct mailbox_settings *set;
+	enum mailbox_info_flags flags;
+	bool child_listed;
+};
+
+ARRAY_DEFINE_TYPE(mailbox_settings, struct mailbox_settings *);
+struct mailbox_list_autocreate_iterate_context {
+	unsigned int idx;
+	struct mailbox_info new_info;
+	ARRAY(struct autocreate_box) boxes;
+	ARRAY_TYPE(mailbox_settings) box_sets;
+	ARRAY_TYPE(mailbox_settings) all_ns_box_sets;
+	HASH_TABLE(char *, char *) duplicate_vnames;
+	bool listing_autoboxes:1;
+};
+
+static inline bool
+mailbox_list_iter_try_delete_noselect(struct mailbox_list_iterate_context *ctx,
+				      const struct mailbox_info *info,
+				      const char *storage_name)
+{
+	if ((info->flags & (MAILBOX_NOSELECT|MAILBOX_NOCHILDREN)) ==
+	    (MAILBOX_NOSELECT|MAILBOX_NOCHILDREN) &&
+	    ctx->list->set.no_noselect) {
+		/* Try to rmdir() all \NoSelect mailbox leafs and
+		   afterwards their parents. */
+		mailbox_list_delete_mailbox_until_root(ctx->list, storage_name);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-iter.c b/src/lib-storage/list/mailbox-list-iter.c
new file mode 100644
index 0000000..4d3d135
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-iter.c
@@ -0,0 +1,1168 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "hash.h"
+#include "imap-match.h"
+#include "mail-storage.h"
+#include "mailbox-tree.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-private.h"
+#include "mailbox-list-iter-private.h"
+
+enum autocreate_match_result {
+	/* list contains the mailbox */
+	AUTOCREATE_MATCH_RESULT_YES		= 0x01,
+	/* list contains children of the mailbox */
+	AUTOCREATE_MATCH_RESULT_CHILDREN	= 0x02,
+	/* list contains parents of the mailbox */
+	AUTOCREATE_MATCH_RESULT_PARENT		= 0x04
+};
+
+struct ns_list_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+	struct mailbox_list_iterate_context *backend_ctx;
+	struct mail_namespace *namespaces, *cur_ns;
+	struct mailbox_list *error_list;
+	pool_t pool;
+	const char **patterns, **patterns_ns_match;
+	enum mail_namespace_type type_mask;
+
+	struct mailbox_info ns_info;
+	struct mailbox_info inbox_info;
+	const struct mailbox_info *pending_backend_info;
+
+	bool cur_ns_prefix_sent:1;
+	bool inbox_list:1;
+	bool inbox_listed:1;
+	bool inbox_seen:1;
+};
+
+static void mailbox_list_ns_iter_failed(struct ns_list_iterate_context *ctx);
+static bool ns_match_next(struct ns_list_iterate_context *ctx, 
+			  struct mail_namespace *ns, const char *pattern);
+static int mailbox_list_match_anything(struct ns_list_iterate_context *ctx,
+				       struct mail_namespace *ns,
+				       const char *prefix);
+
+static struct mailbox_list_iterate_context mailbox_list_iter_failed;
+
+struct mailbox_list_iterate_context *
+mailbox_list_iter_init(struct mailbox_list *list, const char *pattern,
+		       enum mailbox_list_iter_flags flags)
+{
+	const char *patterns[2];
+
+	patterns[0] = pattern;
+	patterns[1] = NULL;
+	return mailbox_list_iter_init_multiple(list, patterns, flags);
+}
+
+int mailbox_list_iter_subscriptions_refresh(struct mailbox_list *list)
+{
+	struct mail_namespace *ns = list->ns;
+
+	if ((ns->flags & NAMESPACE_FLAG_SUBSCRIPTIONS) == 0) {
+		/* no subscriptions in this namespace. find where they are. */
+		ns = mail_namespace_find_subscribable(ns->user->namespaces,
+						      ns->prefix);
+		if (ns == NULL) {
+			/* no subscriptions. avoid crashes by initializing
+			   a subscriptions tree. */
+			if (list->subscriptions == NULL) {
+				char sep = mail_namespace_get_sep(list->ns);
+				list->subscriptions = mailbox_tree_init(sep);
+			}
+			return 0;
+		}
+	}
+	return ns->list->v.subscriptions_refresh(ns->list, list);
+}
+
+static struct mailbox_settings *
+mailbox_settings_add_ns_prefix(pool_t pool, struct mail_namespace *ns,
+			       struct mailbox_settings *in_set)
+{
+	struct mailbox_settings *out_set;
+
+	if (ns->prefix_len == 0 || strcasecmp(in_set->name, "INBOX") == 0)
+		return in_set;
+
+	out_set = p_new(pool, struct mailbox_settings, 1);
+	*out_set = *in_set;
+	if (*in_set->name == '\0') {
+		/* namespace prefix itself */
+		out_set->name = p_strndup(pool, ns->prefix, ns->prefix_len-1);
+	} else {
+		out_set->name =
+			p_strconcat(pool, ns->prefix, in_set->name, NULL);
+	}
+	return out_set;
+}
+
+static void
+mailbox_list_iter_init_autocreate(struct mailbox_list_iterate_context *ctx)
+{
+	struct mail_namespace *ns = ctx->list->ns;
+	struct mailbox_list_autocreate_iterate_context *actx;
+	struct mailbox_settings *const *box_sets, *set;
+	struct autocreate_box *autobox;
+	unsigned int i, count;
+
+	if (!array_is_created(&ns->set->mailboxes))
+		return;
+	box_sets = array_get(&ns->set->mailboxes, &count);
+	if (count == 0)
+		return;
+
+	actx = p_new(ctx->pool, struct mailbox_list_autocreate_iterate_context, 1);
+	ctx->autocreate_ctx = actx;
+	hash_table_create(&actx->duplicate_vnames, ctx->pool, 0,
+			  str_hash, strcmp);
+
+	/* build the list of mailboxes we need to consider as existing */
+	p_array_init(&actx->boxes, ctx->pool, 16);
+	p_array_init(&actx->box_sets, ctx->pool, 16);
+	p_array_init(&actx->all_ns_box_sets, ctx->pool, 16);
+	for (i = 0; i < count; i++) {
+		if (strcmp(box_sets[i]->autocreate, MAILBOX_SET_AUTO_NO) == 0)
+			continue;
+
+		set = mailbox_settings_add_ns_prefix(ctx->pool,
+						     ns, box_sets[i]);
+
+		/* autocreate mailbox belongs to listed namespace */
+		array_push_back(&actx->all_ns_box_sets, &set);
+		if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0 ||
+		    strcmp(set->autocreate, MAILBOX_SET_AUTO_SUBSCRIBE) == 0) {
+			array_push_back(&actx->box_sets, &set);
+			autobox = array_append_space(&actx->boxes);
+			autobox->name = set->name;
+			autobox->set = set;
+			if (strcasecmp(autobox->name, "INBOX") == 0) {
+				/* make sure duplicate INBOX/Inbox/etc.
+				   won't get created */
+				autobox->name = "INBOX";
+			}
+		}
+	}
+}
+
+struct mailbox_list_iterate_context *
+mailbox_list_iter_init_multiple(struct mailbox_list *list,
+				const char *const *patterns,
+				enum mailbox_list_iter_flags flags)
+{
+	struct mailbox_list_iterate_context *ctx;
+
+	i_assert(*patterns != NULL);
+
+	if ((flags & (MAILBOX_LIST_ITER_SELECT_SUBSCRIBED |
+		      MAILBOX_LIST_ITER_RETURN_SUBSCRIBED)) != 0) {
+		if (mailbox_list_iter_subscriptions_refresh(list) < 0)
+			return &mailbox_list_iter_failed;
+	}
+
+	ctx = list->v.iter_init(list, patterns, flags);
+	if ((flags & MAILBOX_LIST_ITER_NO_AUTO_BOXES) == 0)
+		mailbox_list_iter_init_autocreate(ctx);
+	return ctx;
+}
+
+static bool
+ns_match_simple(struct ns_list_iterate_context *ctx, struct mail_namespace *ns)
+{
+	if ((ctx->type_mask & ns->type) == 0)
+		return FALSE;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SKIP_ALIASES) != 0) {
+		if (ns->alias_for != NULL)
+			return FALSE;
+	}
+	return TRUE;
+}
+
+static bool
+ns_is_match_within_ns(struct ns_list_iterate_context *ctx, 
+		      struct mail_namespace *ns, const char *prefix_without_sep,
+		      const char *pattern, enum imap_match_result result)
+{
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_STAR_WITHIN_NS) == 0) {
+		switch (result) {
+		case IMAP_MATCH_YES:
+		case IMAP_MATCH_CHILDREN:
+			return TRUE;
+		case IMAP_MATCH_NO:
+		case IMAP_MATCH_PARENT:
+			break;
+		}
+		return FALSE;
+	}
+
+	switch (result) {
+	case IMAP_MATCH_YES:
+		/* allow matching prefix only when it's done without
+		   wildcards */
+		if (strcmp(prefix_without_sep, pattern) == 0)
+			return TRUE;
+		break;
+	case IMAP_MATCH_CHILDREN: {
+		/* allow this only if there isn't another namespace
+		   with longer prefix that matches this pattern
+		   (namespaces are sorted by prefix length) */
+		struct mail_namespace *tmp;
+
+		T_BEGIN {
+			for (tmp = ns->next; tmp != NULL; tmp = tmp->next) {
+				if (ns_match_simple(ctx, tmp) &&
+				    ns_match_next(ctx, tmp, pattern))
+					break;
+			}
+		} T_END;
+		if (tmp == NULL)
+			return TRUE;
+		break;
+	}
+	case IMAP_MATCH_NO:
+	case IMAP_MATCH_PARENT:
+		break;
+	}
+	return FALSE;
+}
+
+static bool list_pattern_has_wildcards(const char *pattern)
+{
+	for (; *pattern != '\0'; pattern++) {
+		if (*pattern == '%' || *pattern == '*')
+			return TRUE;
+	}
+	return FALSE;
+}
+
+static bool ns_match_next(struct ns_list_iterate_context *ctx, 
+			  struct mail_namespace *ns, const char *pattern)
+{
+	struct imap_match_glob *glob;
+	enum imap_match_result result;
+	const char *prefix_without_sep;
+	size_t len;
+
+	len = ns->prefix_len;
+	if (len > 0 && ns->prefix[len-1] == mail_namespace_get_sep(ns))
+		len--;
+
+	if ((ns->flags & (NAMESPACE_FLAG_LIST_PREFIX |
+			  NAMESPACE_FLAG_LIST_CHILDREN)) == 0) {
+		/* non-listable namespace matches only with exact prefix */
+		if (strncmp(ns->prefix, pattern, ns->prefix_len) != 0)
+			return FALSE;
+		/* with prefix="", list=no we don't want to show anything,
+		   except when the client explicitly lists a mailbox without
+		   wildcards (e.g. LIST "" mailbox). this is mainly useful
+		   for working around client bugs (and supporting a specific
+		   IMAP client behavior that's not exactly buggy but not very
+		   good IMAP behavior either). */
+		if (ns->prefix_len == 0 && list_pattern_has_wildcards(pattern))
+			return FALSE;
+	}
+
+	prefix_without_sep = t_strndup(ns->prefix, len);
+	if (*prefix_without_sep == '\0')
+		result = IMAP_MATCH_CHILDREN;
+	else {
+		glob = imap_match_init(pool_datastack_create(), pattern,
+				       TRUE, mail_namespace_get_sep(ns));
+		result = imap_match(glob, prefix_without_sep);
+	}
+
+	return ns_is_match_within_ns(ctx, ns, prefix_without_sep,
+				     pattern, result);
+}
+
+static bool
+mailbox_list_ns_match_patterns(struct ns_list_iterate_context *ctx)
+{
+	struct mail_namespace *ns = ctx->cur_ns;
+	unsigned int i;
+
+	if (!ns_match_simple(ctx, ns))
+		return FALSE;
+
+	/* filter out namespaces whose prefix doesn't match. this same code
+	   handles both with and without STAR_WITHIN_NS, so the "without" case
+	   is slower than necessary, but this shouldn't matter much */
+	T_BEGIN {
+		for (i = 0; ctx->patterns_ns_match[i] != NULL; i++) {
+			if (ns_match_next(ctx, ns, ctx->patterns_ns_match[i]))
+				break;
+		}
+	} T_END;
+
+	return ctx->patterns_ns_match[i] != NULL;
+}
+
+static bool
+iter_next_try_prefix_pattern(struct ns_list_iterate_context *ctx,
+			     struct mail_namespace *ns, const char *pattern)
+{
+	struct imap_match_glob *glob;
+	enum imap_match_result result;
+	const char *prefix_without_sep;
+
+	i_assert(ns->prefix_len > 0);
+
+	if ((ns->flags & (NAMESPACE_FLAG_LIST_PREFIX |
+			  NAMESPACE_FLAG_LIST_CHILDREN)) == 0) {
+		/* non-listable namespace matches only with exact prefix */
+		if (strncmp(ns->prefix, pattern, ns->prefix_len) != 0)
+			return FALSE;
+	}
+
+	prefix_without_sep = t_strndup(ns->prefix, ns->prefix_len-1);
+	glob = imap_match_init(pool_datastack_create(), pattern,
+			       TRUE, mail_namespace_get_sep(ns));
+	result = imap_match(glob, prefix_without_sep);
+	return result == IMAP_MATCH_YES &&
+		ns_is_match_within_ns(ctx, ns, prefix_without_sep,
+				      pattern, result);
+}
+
+static bool
+mailbox_list_ns_prefix_match(struct ns_list_iterate_context *ctx,
+			     struct mail_namespace *ns)
+{
+	unsigned int i;
+	bool ret = FALSE;
+
+	for (i = 0; ctx->patterns_ns_match[i] != NULL; i++) {
+		T_BEGIN {
+			ret = iter_next_try_prefix_pattern(ctx, ns,
+						ctx->patterns_ns_match[i]);
+		} T_END;
+		if (ret)
+			break;
+	}
+	return ret;
+}
+
+static int
+ns_prefix_is_visible(struct ns_list_iterate_context *ctx,
+		     struct mail_namespace *ns)
+{
+	int ret;
+
+	if ((ns->flags & NAMESPACE_FLAG_LIST_PREFIX) != 0)
+		return 1;
+	if ((ns->flags & NAMESPACE_FLAG_LIST_CHILDREN) != 0) {
+		if ((ret = mailbox_list_match_anything(ctx, ns, ns->prefix)) != 0)
+			return ret;
+	}
+	return 0;
+}
+
+static int
+ns_prefix_has_visible_child_namespace(struct ns_list_iterate_context *ctx,
+				      const char *prefix)
+{
+	struct mail_namespace *ns;
+	size_t prefix_len = strlen(prefix);
+	int ret;
+
+	for (ns = ctx->namespaces; ns != NULL; ns = ns->next) {
+		if (ns->prefix_len > prefix_len &&
+		    strncmp(ns->prefix, prefix, prefix_len) == 0) {
+			ret = ns_prefix_is_visible(ctx, ns);
+			if (ret != 0)
+				return ret;
+		}
+	}
+	return 0;
+}
+
+static bool
+mailbox_ns_prefix_is_shared_inbox(struct mail_namespace *ns)
+{
+	return ns->type == MAIL_NAMESPACE_TYPE_SHARED &&
+		(ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0 &&
+		!ns->list->mail_set->mail_shared_explicit_inbox;
+}
+
+static bool
+mailbox_is_shared_inbox(struct mail_namespace *ns, const char *vname)
+{
+	return mailbox_ns_prefix_is_shared_inbox(ns) &&
+		strncmp(ns->prefix, vname, ns->prefix_len-1) == 0 &&
+		vname[ns->prefix_len-1] == '\0';
+}
+
+static int
+mailbox_list_match_anything(struct ns_list_iterate_context *ctx,
+			    struct mail_namespace *ns, const char *prefix)
+{
+	enum mailbox_list_iter_flags list_flags =
+		MAILBOX_LIST_ITER_RETURN_NO_FLAGS;
+	struct mailbox_list_iterate_context *list_iter;
+	const struct mailbox_info *info;
+	const char *pattern;
+	int ret;
+
+	if ((ret = ns_prefix_has_visible_child_namespace(ctx, prefix)) != 0)
+		return ret;
+
+	pattern = t_strconcat(prefix, "%", NULL);
+	list_iter = mailbox_list_iter_init(ns->list, pattern, list_flags);
+	info = mailbox_list_iter_next(list_iter);
+	if (info != NULL && mailbox_ns_prefix_is_shared_inbox(ns) &&
+	    mailbox_is_shared_inbox(ns, info->vname)) {
+		/* we don't want to see this, try the next one */
+		info = mailbox_list_iter_next(list_iter);
+	}
+	ret = info != NULL ? 1 : 0;
+	if (mailbox_list_iter_deinit(&list_iter) < 0) {
+		if (ret == 0)
+			ret = -1;
+	}
+	return ret;
+}
+
+static bool
+mailbox_ns_prefix_check_selection_criteria(struct ns_list_iterate_context *ctx)
+{
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0) {
+		if ((ctx->ns_info.flags & MAILBOX_SUBSCRIBED) != 0)
+			return TRUE;
+		if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SELECT_RECURSIVEMATCH) != 0 &&
+		    (ctx->ns_info.flags & MAILBOX_CHILD_SUBSCRIBED) != 0)
+			return TRUE;
+		return FALSE;
+	}
+	return TRUE;
+}
+
+static bool
+mailbox_list_ns_prefix_return(struct ns_list_iterate_context *ctx,
+			      struct mail_namespace *ns, bool has_children)
+{
+	struct mailbox *box;
+	enum mailbox_existence existence;
+	int ret;
+
+	if (strncasecmp(ns->prefix, "INBOX", 5) == 0 &&
+	    ns->prefix[5] == mail_namespace_get_sep(ns)) {
+		/* prefix=INBOX/ (or prefix=INBOX/something/) namespace exists.
+		   so we can create children to INBOX. */
+		ctx->inbox_info.flags &= ENUM_NEGATE(MAILBOX_NOINFERIORS);
+	}
+
+	if (ns->prefix_len == 0 || !mailbox_list_ns_prefix_match(ctx, ns))
+		return FALSE;
+
+	i_zero(&ctx->ns_info);
+	ctx->ns_info.ns = ns;
+	ctx->ns_info.vname = p_strndup(ctx->pool, ns->prefix,
+				       ns->prefix_len-1);
+	if (ns->special_use_mailboxes)
+		ctx->ns_info.flags |= MAILBOX_CHILD_SPECIALUSE;
+
+	if (strcasecmp(ctx->ns_info.vname, "INBOX") == 0) {
+		i_assert(!ctx->inbox_listed);
+		ctx->inbox_listed = TRUE;
+		ctx->ns_info.flags |= ctx->inbox_info.flags | MAILBOX_SELECT;
+	}
+
+	if ((ctx->ctx.flags & (MAILBOX_LIST_ITER_RETURN_SUBSCRIBED |
+			       MAILBOX_LIST_ITER_SELECT_SUBSCRIBED)) != 0) {
+		/* Refresh subscriptions first, this won't cause a duplicate
+		   call later on as this is only called when the namespace's
+		   children definitely don't match */
+		if (mailbox_list_iter_subscriptions_refresh(ns->list) < 0) {
+			mailbox_list_ns_iter_failed(ctx);
+			return FALSE;
+		}
+		mailbox_list_set_subscription_flags(ns->list,
+						    ctx->ns_info.vname,
+						    &ctx->ns_info.flags);
+	}
+	if (!mailbox_ns_prefix_check_selection_criteria(ctx))
+		return FALSE;
+
+	/* see if the namespace has children */
+	if (has_children)
+		ctx->ns_info.flags |= MAILBOX_CHILDREN;
+	else if ((ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_CHILDREN) != 0 ||
+		 (ns->flags & NAMESPACE_FLAG_LIST_CHILDREN) != 0) {
+		/* need to check this explicitly */
+		if ((ret = mailbox_list_match_anything(ctx, ns, ns->prefix)) > 0)
+			ctx->ns_info.flags |= MAILBOX_CHILDREN;
+		else if (ret == 0) {
+			if ((ns->flags & NAMESPACE_FLAG_LIST_CHILDREN) != 0 &&
+			    !mailbox_ns_prefix_is_shared_inbox(ns)) {
+				/* no children -> not visible */
+				return FALSE;
+			}
+			ctx->ns_info.flags |= MAILBOX_NOCHILDREN;
+		}
+	}
+
+	if ((ctx->ns_info.flags & MAILBOX_SELECT) == 0) {
+		/* see if namespace prefix is selectable */
+		box = mailbox_alloc(ns->list, ctx->ns_info.vname, 0);
+		if (mailbox_exists(box, TRUE, &existence) == 0 &&
+		    existence == MAILBOX_EXISTENCE_SELECT)
+			ctx->ns_info.flags |= MAILBOX_SELECT;
+		else
+			ctx->ns_info.flags |= MAILBOX_NONEXISTENT;
+		mailbox_free(&box);
+	}
+	return TRUE;
+}
+
+static void inbox_set_children_flags(struct ns_list_iterate_context *ctx)
+{
+	struct mail_namespace *ns;
+	const char *prefix;
+	int ret;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_RETURN_NO_FLAGS) != 0)
+		return;
+	if ((ctx->inbox_info.flags & (MAILBOX_CHILDREN | MAILBOX_NOINFERIORS |
+				      MAILBOX_NOCHILDREN)) != 0)
+		return;
+
+	ns = mail_namespace_find_prefix(ctx->namespaces, "");
+	if (ns == NULL || (ns->flags & NAMESPACE_FLAG_UNUSABLE) != 0) {
+		/* prefix="" namespace doesn't exist, and neither does
+		   anything beginning with prefix=INBOX/ (we checked this
+		   earlier). there's no way to create children for INBOX. */
+		ctx->inbox_info.flags |= MAILBOX_NOINFERIORS;
+		return;
+	}
+
+	/* INBOX namespace doesn't exist and we didn't see any children listed
+	   for INBOX. this could be because there truly aren't any children,
+	   or that the list patterns just didn't match them. */
+	prefix = t_strdup_printf("INBOX%c",
+				 mail_namespace_get_sep(ctx->inbox_info.ns));
+	ret = mailbox_list_match_anything(ctx, ctx->inbox_info.ns, prefix);
+	if (ret > 0)
+		ctx->inbox_info.flags |= MAILBOX_CHILDREN;
+	else if (ret == 0)
+		ctx->inbox_info.flags |= MAILBOX_NOCHILDREN;
+}
+
+static void mailbox_list_ns_iter_failed(struct ns_list_iterate_context *ctx)
+{
+	enum mail_error error;
+	const char *errstr;
+
+	if (ctx->cur_ns->list != ctx->error_list) {
+		errstr = mailbox_list_get_last_error(ctx->cur_ns->list, &error);
+		mailbox_list_set_error(ctx->error_list, error, errstr);
+	}
+	ctx->ctx.failed = TRUE;
+}
+
+static bool
+mailbox_list_ns_iter_try_next(struct mailbox_list_iterate_context *_ctx,
+			      const struct mailbox_info **info_r)
+{
+	struct ns_list_iterate_context *ctx =
+		(struct ns_list_iterate_context *)_ctx;
+	struct mail_namespace *ns;
+	const struct mailbox_info *info;
+	bool has_children;
+
+	if (ctx->cur_ns == NULL) {
+		if (!ctx->inbox_listed && ctx->inbox_list && !_ctx->failed &&
+		    ((_ctx->flags & MAILBOX_LIST_ITER_NO_AUTO_BOXES) == 0 ||
+		     ctx->inbox_seen)) {
+			/* send delayed INBOX reply */
+			ctx->inbox_listed = TRUE;
+			inbox_set_children_flags(ctx);
+			*info_r = &ctx->inbox_info;
+			return TRUE;
+		}
+		*info_r = NULL;
+		return TRUE;
+	}
+
+	if (ctx->backend_ctx == NULL) {
+		i_assert(ctx->pending_backend_info == NULL);
+		if (!mailbox_list_ns_match_patterns(ctx)) {
+			/* namespace's children don't match the patterns,
+			   but the namespace prefix itself might */
+			ns = ctx->cur_ns;
+			ctx->cur_ns = ctx->cur_ns->next;
+			if (mailbox_list_ns_prefix_return(ctx, ns, FALSE)) {
+				*info_r = &ctx->ns_info;
+				return TRUE;
+			}
+			return FALSE;
+		}
+		/* start listing this namespace's mailboxes */
+		ctx->backend_ctx =
+			mailbox_list_iter_init_multiple(ctx->cur_ns->list,
+							ctx->patterns,
+							_ctx->flags);
+		ctx->cur_ns_prefix_sent = FALSE;
+	}
+	if (ctx->pending_backend_info == NULL)
+		info = mailbox_list_iter_next(ctx->backend_ctx);
+	else {
+		info = ctx->pending_backend_info;
+		ctx->pending_backend_info = NULL;
+	}
+	if (!ctx->cur_ns_prefix_sent) {
+		/* delayed sending of namespace prefix */
+		ctx->cur_ns_prefix_sent = TRUE;
+		has_children = info != NULL &&
+			!mailbox_is_shared_inbox(info->ns, info->vname);
+		if (mailbox_list_ns_prefix_return(ctx, ctx->cur_ns,
+						  has_children)) {
+			ctx->pending_backend_info = info;
+			*info_r = &ctx->ns_info;
+			return TRUE;
+		}
+	}
+	if (info != NULL) {
+		if (strcasecmp(info->vname, "INBOX") == 0 && ctx->inbox_list) {
+			/* delay sending INBOX reply. we already saved its
+			   flags at init stage, except for \Noinferiors
+			   and subscription states */
+			ctx->inbox_seen = TRUE;
+			ctx->inbox_info.flags |=
+				(info->flags & (MAILBOX_NOINFERIORS |
+						MAILBOX_SUBSCRIBED |
+						MAILBOX_CHILD_SUBSCRIBED));
+			return FALSE;
+		}
+		if (strncasecmp(info->vname, "INBOX", 5) == 0 &&
+		    info->vname[5] == mail_namespace_get_sep(info->ns)) {
+			/* we know now that INBOX has children */
+			ctx->inbox_info.flags |= MAILBOX_CHILDREN;
+			ctx->inbox_info.flags &= ENUM_NEGATE(MAILBOX_NOINFERIORS);
+		}
+		if (info->ns->prefix_len > 0 &&
+		    strncmp(info->vname, info->ns->prefix,
+			    info->ns->prefix_len-1) == 0 &&
+		    info->vname[info->ns->prefix_len-1] == '\0') {
+			/* this is an entry for namespace prefix, which we
+			   already returned. (e.g. shared/$user/INBOX entry
+			   returned as shared/$user, or when listing
+			   subscribed namespace prefix). */
+			return FALSE;
+		}
+
+		*info_r = info;
+		return TRUE;
+	}
+
+	/* finished with this namespace */
+	if (mailbox_list_iter_deinit(&ctx->backend_ctx) < 0)
+		mailbox_list_ns_iter_failed(ctx);
+	ctx->cur_ns = ctx->cur_ns->next;
+	return FALSE;
+}
+
+static const struct mailbox_info *
+mailbox_list_ns_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	const struct mailbox_info *info = NULL;
+
+	while (!mailbox_list_ns_iter_try_next(_ctx, &info)) ;
+	return info;
+}
+
+static int
+mailbox_list_ns_iter_deinit(struct mailbox_list_iterate_context *_ctx)
+{
+	struct ns_list_iterate_context *ctx =
+		(struct ns_list_iterate_context *)_ctx;
+	int ret;
+
+	if (ctx->backend_ctx != NULL) {
+		if (mailbox_list_iter_deinit(&ctx->backend_ctx) < 0)
+			mailbox_list_ns_iter_failed(ctx);
+	}
+	ret = _ctx->failed ? -1 : 0;
+	pool_unref(&ctx->pool);
+	return ret;
+}
+
+static const char **
+dup_patterns_without_stars(pool_t pool, const char *const *patterns,
+			   unsigned int count)
+{
+	const char **dup;
+	unsigned int i;
+
+	dup = p_new(pool, const char *, count + 1);
+	for (i = 0; i < count; i++) {
+		char *p = p_strdup(pool, patterns[i]);
+		dup[i] = p;
+
+		for (; *p != '\0'; p++) {
+			if (*p == '*')
+				*p = '%';
+		}
+	}
+	return dup;
+}
+
+static bool
+patterns_match_inbox(struct mail_namespace *namespaces,
+		     const char *const *patterns)
+{
+	struct mail_namespace *ns = mail_namespace_find_inbox(namespaces);
+	struct imap_match_glob *glob;
+
+	glob = imap_match_init_multiple(pool_datastack_create(), patterns,
+					TRUE, mail_namespace_get_sep(ns));
+	return imap_match(glob, "INBOX") == IMAP_MATCH_YES;
+}
+
+static int inbox_info_init(struct ns_list_iterate_context *ctx,
+			   struct mail_namespace *namespaces)
+{
+	enum mailbox_info_flags flags;
+	int ret;
+
+	ctx->inbox_info.vname = "INBOX";
+	ctx->inbox_info.ns = mail_namespace_find_inbox(namespaces);
+	i_assert(ctx->inbox_info.ns != NULL);
+
+	if ((ret = mailbox_list_mailbox(ctx->inbox_info.ns->list, "INBOX", &flags)) > 0)
+		ctx->inbox_info.flags = flags;
+	else if (ret < 0) {
+		ctx->cur_ns = ctx->inbox_info.ns;
+		mailbox_list_ns_iter_failed(ctx);
+	}
+	return ret;
+}
+
+struct mailbox_list_iterate_context *
+mailbox_list_iter_init_namespaces(struct mail_namespace *namespaces,
+				  const char *const *patterns,
+				  enum mail_namespace_type type_mask,
+				  enum mailbox_list_iter_flags flags)
+{
+	struct ns_list_iterate_context *ctx;
+	unsigned int i, count;
+	pool_t pool;
+
+	i_assert(namespaces != NULL);
+
+	pool = pool_alloconly_create("mailbox list namespaces", 1024);
+	ctx = p_new(pool, struct ns_list_iterate_context, 1);
+	ctx->pool = pool;
+	ctx->type_mask = type_mask;
+	ctx->ctx.flags = flags;
+	ctx->ctx.list = p_new(pool, struct mailbox_list, 1);
+	ctx->ctx.list->v.iter_next = mailbox_list_ns_iter_next;
+	ctx->ctx.list->v.iter_deinit = mailbox_list_ns_iter_deinit;
+	ctx->namespaces = namespaces;
+	ctx->error_list = namespaces->list;
+
+	count = str_array_length(patterns);
+	ctx->patterns = p_new(pool, const char *, count + 1);
+	for (i = 0; i < count; i++)
+		ctx->patterns[i] = p_strdup(pool, patterns[i]);
+	if (patterns_match_inbox(namespaces, ctx->patterns) &&
+	    (flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0) {
+		/* we're going to list the INBOX. get its own flags (i.e. not
+		   [no]children) immediately, so if we end up seeing something
+		   else called INBOX (e.g. namespace prefix) we can show it
+		   immediately with the proper flags. */
+		ctx->inbox_list = TRUE;
+		if (inbox_info_init(ctx, namespaces) < 0) {
+			pool_unref(&pool);
+			return &mailbox_list_iter_failed;
+		}
+	}
+
+	if ((flags & MAILBOX_LIST_ITER_STAR_WITHIN_NS) != 0) {
+		/* create copies of patterns with '*' wildcard changed to '%'.
+		   this is used only when checking which namespaces to list */
+		ctx->patterns_ns_match =
+			dup_patterns_without_stars(pool, ctx->patterns, count);
+	} else {
+		ctx->patterns_ns_match = ctx->patterns;
+	}
+
+	ctx->cur_ns = namespaces;
+	ctx->ctx.list->ns = namespaces;
+	return &ctx->ctx;
+}
+
+static enum autocreate_match_result
+autocreate_box_match(const ARRAY_TYPE(mailbox_settings) *boxes,
+		     struct mail_namespace *ns, const char *name,
+		     bool only_subscribed, unsigned int *idx_r)
+{
+	struct mailbox_settings *const *sets;
+	unsigned int i, count;
+	size_t len, name_len = strlen(name);
+	enum autocreate_match_result result = 0;
+	char sep = mail_namespace_get_sep(ns);
+
+	*idx_r = UINT_MAX;
+
+	sets = array_get(boxes, &count);
+	for (i = 0; i < count; i++) {
+		if (only_subscribed &&
+		    strcmp(sets[i]->autocreate, MAILBOX_SET_AUTO_SUBSCRIBE) != 0)
+			continue;
+		len = I_MIN(name_len, strlen(sets[i]->name));
+		if (strncmp(name, sets[i]->name, len) != 0)
+			continue;
+
+		if (name[len] == '\0' && sets[i]->name[len] == '\0') {
+			result |= AUTOCREATE_MATCH_RESULT_YES;
+			*idx_r = i;
+		} else if (name[len] == '\0' && sets[i]->name[len] == sep)
+			result |= AUTOCREATE_MATCH_RESULT_CHILDREN;
+		else if (name[len] == sep && sets[i]->name[len] == '\0')
+			result |= AUTOCREATE_MATCH_RESULT_PARENT;
+	}
+	return result;
+}
+
+const struct mailbox_info *
+mailbox_list_iter_autocreate_filter(struct mailbox_list_iterate_context *ctx,
+				    const struct mailbox_info *_info)
+{
+	struct mailbox_list_autocreate_iterate_context *actx =
+		ctx->autocreate_ctx;
+	if (actx == NULL || _info == NULL)
+		return _info;
+	actx->new_info = *_info;
+	struct mailbox_info *info = &actx->new_info;
+	enum autocreate_match_result match, match2;
+	unsigned int idx;
+
+	match = autocreate_box_match(&actx->box_sets, ctx->list->ns,
+				     info->vname, FALSE, &idx);
+
+	if (!actx->listing_autoboxes) {
+		if ((match & AUTOCREATE_MATCH_RESULT_YES) != 0) {
+			/* we have an exact match in the list.
+			   don't list it at the end. */
+			array_delete(&actx->boxes, idx, 1);
+			array_delete(&actx->box_sets, idx, 1);
+		}
+		if ((match & AUTOCREATE_MATCH_RESULT_CHILDREN) != 0 &&
+		    hash_table_lookup(actx->duplicate_vnames, info->vname) == NULL) {
+			/* Prevent autocreate-iteration from adding this
+			   mailbox as a duplicate. For example we're listing %
+			   and we're here because "foo" was found. However,
+			   there's also "foo/bar" with auto=create. We're
+			   telling here to the autocreate iteration code that
+			   "foo" was already found and it doesn't need to add
+			   it again. */
+			char *vname = p_strdup(ctx->pool, info->vname);
+			hash_table_insert(actx->duplicate_vnames, vname, vname);
+		}
+	}
+
+	if ((match & AUTOCREATE_MATCH_RESULT_CHILDREN) != 0) {
+		if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+			info->flags |= MAILBOX_CHILD_SUBSCRIBED;
+		else {
+			info->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+			info->flags |= MAILBOX_CHILDREN;
+		}
+	}
+
+	/* make sure the mailbox existence flags are correct. */
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0)
+		match2 = match;
+	else {
+		match2 = autocreate_box_match(&actx->all_ns_box_sets,
+					      ctx->list->ns, info->vname,
+					      FALSE, &idx);
+	}
+	if ((match2 & AUTOCREATE_MATCH_RESULT_YES) != 0)
+		info->flags &= ENUM_NEGATE(MAILBOX_NONEXISTENT);
+	if ((match2 & AUTOCREATE_MATCH_RESULT_CHILDREN) != 0) {
+		info->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+		info->flags |= MAILBOX_CHILDREN;
+	}
+
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0 &&
+	    (ctx->flags & MAILBOX_LIST_ITER_RETURN_SUBSCRIBED) != 0) {
+		/* we're listing all mailboxes and want \Subscribed flag */
+		match2 = autocreate_box_match(&actx->all_ns_box_sets,
+					      ctx->list->ns, info->vname,
+					      TRUE, &idx);
+		if ((match2 & AUTOCREATE_MATCH_RESULT_YES) != 0) {
+			/* mailbox is also marked as autosubscribe */
+			info->flags |= MAILBOX_SUBSCRIBED;
+		}
+		if ((match2 & AUTOCREATE_MATCH_RESULT_CHILDREN) != 0) {
+			/* mailbox also has a children marked as
+			   autosubscribe */
+			info->flags |= MAILBOX_CHILD_SUBSCRIBED;
+		}
+	}
+
+	if ((match & AUTOCREATE_MATCH_RESULT_PARENT) != 0) {
+		/* there are autocreate parent boxes.
+		   set their children flag states. */
+		struct autocreate_box *autobox;
+		size_t name_len;
+		char sep = mail_namespace_get_sep(ctx->list->ns);
+
+		array_foreach_modifiable(&actx->boxes, autobox) {
+			name_len = strlen(autobox->name);
+			if (!str_begins(info->vname, autobox->name) ||
+			    info->vname[name_len] != sep)
+				continue;
+
+			if ((info->flags & MAILBOX_NONEXISTENT) == 0)
+				autobox->flags |= MAILBOX_CHILDREN;
+			if ((info->flags & MAILBOX_SUBSCRIBED) != 0)
+				autobox->flags |= MAILBOX_CHILD_SUBSCRIBED;
+			autobox->child_listed = TRUE;
+		}
+	}
+	return info;
+}
+
+static bool autocreate_iter_autobox(struct mailbox_list_iterate_context *ctx,
+				    const struct autocreate_box *autobox)
+{
+	struct mailbox_list_autocreate_iterate_context *actx =
+		ctx->autocreate_ctx;
+	enum imap_match_result match;
+
+	i_zero(&actx->new_info);
+	actx->new_info.ns = ctx->list->ns;
+	actx->new_info.vname = autobox->name;
+	actx->new_info.flags = autobox->flags;
+
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0)
+		actx->new_info.flags |= MAILBOX_SUBSCRIBED;
+
+	if ((actx->new_info.flags & MAILBOX_CHILDREN) == 0) {
+		if ((ctx->list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0 &&
+		    ctx->list->set.maildir_name[0] == '\0') {
+			/* mailbox format using files (e.g. mbox)
+			   without DIRNAME specified */
+			actx->new_info.flags |= MAILBOX_NOINFERIORS;
+		} else {
+			actx->new_info.flags |= MAILBOX_NOCHILDREN;
+		}
+	}
+
+	match = imap_match(ctx->glob, actx->new_info.vname);
+	if (match == IMAP_MATCH_YES) {
+		actx->new_info.special_use =
+			*autobox->set->special_use == '\0' ? NULL :
+			autobox->set->special_use;
+		return TRUE;
+	}
+	if ((match & IMAP_MATCH_PARENT) != 0 && !autobox->child_listed) {
+		enum mailbox_info_flags old_flags = actx->new_info.flags;
+		char sep = mail_namespace_get_sep(ctx->list->ns);
+		const char *p;
+		char *vname;
+
+		/* e.g. autocreate=foo/bar and we're listing % */
+		actx->new_info.flags = MAILBOX_NONEXISTENT |
+			(old_flags & (MAILBOX_CHILDREN |
+				      MAILBOX_CHILD_SUBSCRIBED));
+		if ((old_flags & MAILBOX_NONEXISTENT) == 0) {
+			actx->new_info.flags |= MAILBOX_CHILDREN;
+			actx->new_info.flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+		}
+		if ((old_flags & MAILBOX_SUBSCRIBED) != 0)
+			actx->new_info.flags |= MAILBOX_CHILD_SUBSCRIBED;
+		do {
+			p = strrchr(actx->new_info.vname, sep);
+			i_assert(p != NULL);
+			actx->new_info.vname = vname =
+				p_strdup_until(ctx->pool,
+					       actx->new_info.vname, p);
+			match = imap_match(ctx->glob, actx->new_info.vname);
+		} while (match != IMAP_MATCH_YES);
+
+		if (hash_table_lookup(actx->duplicate_vnames, vname) == NULL) {
+			hash_table_insert(actx->duplicate_vnames, vname, vname);
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+static const struct mailbox_info *
+mailbox_list_iter_next_call(struct mailbox_list_iterate_context *ctx)
+{
+	const struct mailbox_info *info;
+	const struct mailbox_settings *set;
+
+	info = ctx->list->v.iter_next(ctx);
+	if (info == NULL)
+		return NULL;
+
+	ctx->list->ns->flags |= NAMESPACE_FLAG_USABLE;
+	if ((ctx->flags & MAILBOX_LIST_ITER_RETURN_SPECIALUSE) != 0) {
+		set = mailbox_settings_find(ctx->list->ns, info->vname);
+		if (set != NULL && *set->special_use != '\0') {
+			ctx->specialuse_info = *info;
+			ctx->specialuse_info.special_use =
+				*set->special_use == '\0' ? NULL :
+				set->special_use;
+			info = &ctx->specialuse_info;
+		}
+	}
+
+	return mailbox_list_iter_autocreate_filter(ctx, info);
+}
+
+const struct mailbox_info *
+mailbox_list_iter_default_next(struct mailbox_list_iterate_context *ctx)
+{
+	struct mailbox_list_autocreate_iterate_context *actx =
+		ctx->autocreate_ctx;
+	const struct autocreate_box *autoboxes, *autobox;
+	unsigned int count;
+
+	if (actx == NULL)
+		return NULL;
+
+	/* do not drop boxes anymore */
+	actx->listing_autoboxes = TRUE;
+
+	/* list missing mailboxes */
+	autoboxes = array_get(&actx->boxes, &count);
+	while (actx->idx < count) {
+		autobox = &autoboxes[actx->idx++];
+		if (autocreate_iter_autobox(ctx, autobox))
+			return &actx->new_info;
+	}
+	i_assert(array_count(&actx->boxes) == array_count(&actx->box_sets));
+	return NULL;
+}
+
+static bool
+special_use_selection(struct mailbox_list_iterate_context *ctx,
+		      const struct mailbox_info *info)
+{
+	if ((ctx->flags & MAILBOX_LIST_ITER_SELECT_RECURSIVEMATCH) != 0 &&
+	    (ctx->flags & MAILBOX_LIST_ITER_SELECT_SPECIALUSE) != 0) {
+		/* LIST (SPECIAL-USE RECURSIVEMATCH) used. for now we support
+		   this only for namespace prefixes */
+		if ((info->flags & MAILBOX_CHILD_SPECIALUSE) != 0)
+			return TRUE;
+	}
+	return (ctx->flags & MAILBOX_LIST_ITER_SELECT_SPECIALUSE) == 0 ||
+		info->special_use != NULL;
+}
+
+const struct mailbox_info *
+mailbox_list_iter_next(struct mailbox_list_iterate_context *ctx)
+{
+	const struct mailbox_info *info;
+
+	if (ctx == &mailbox_list_iter_failed)
+		return NULL;
+	do {
+		T_BEGIN {
+			info = mailbox_list_iter_next_call(ctx);
+		} T_END;
+	} while (info != NULL && !special_use_selection(ctx, info));
+	return info;
+}
+
+int mailbox_list_iter_deinit(struct mailbox_list_iterate_context **_ctx)
+{
+	struct mailbox_list_iterate_context *ctx = *_ctx;
+
+	*_ctx = NULL;
+
+	if (ctx == &mailbox_list_iter_failed)
+		return -1;
+	if (ctx->autocreate_ctx != NULL)
+		hash_table_destroy(&ctx->autocreate_ctx->duplicate_vnames);
+	return ctx->list->v.iter_deinit(ctx);
+}
+
+static void node_fix_parents(struct mailbox_node *node)
+{
+	/* If we happened to create any of the parents, we need to mark them
+	   nonexistent. */
+	node = node->parent;
+	for (; node != NULL; node = node->parent) {
+		if ((node->flags & MAILBOX_MATCHED) == 0)
+			node->flags |= MAILBOX_NONEXISTENT;
+	}
+}
+
+static void
+mailbox_list_iter_update_real(struct mailbox_list_iter_update_context *ctx,
+			      const char *name)
+{
+	struct mail_namespace *ns = ctx->iter_ctx->list->ns;
+	struct mailbox_node *node;
+	enum mailbox_info_flags create_flags, always_flags;
+	enum imap_match_result match;
+	const char *p;
+	bool created, add_matched;
+
+	create_flags = MAILBOX_NOCHILDREN;
+	always_flags = ctx->leaf_flags;
+	add_matched = TRUE;
+
+	for (;;) {
+		created = FALSE;
+		match = imap_match(ctx->glob, name);
+		if (match == IMAP_MATCH_YES) {
+			node = ctx->update_only ?
+				mailbox_tree_lookup(ctx->tree_ctx, name) :
+				mailbox_tree_get(ctx->tree_ctx, name, &created);
+			if (created) {
+				node->flags = create_flags;
+				if (create_flags != 0)
+					node_fix_parents(node);
+			}
+			if (node != NULL) {
+				if (!ctx->update_only && add_matched)
+					node->flags |= MAILBOX_MATCHED;
+				if ((always_flags & MAILBOX_CHILDREN) != 0)
+					node->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+				node->flags |= always_flags;
+			}
+			/* We don't want to show the parent mailboxes unless
+			   something else matches them, but if they are matched
+			   we want to show them having child subscriptions */
+			add_matched = FALSE;
+		} else {
+			if ((match & IMAP_MATCH_PARENT) == 0)
+				break;
+			/* We've a (possibly) non-subscribed parent mailbox
+			   which has a subscribed child mailbox. Make sure we
+			   return the parent mailbox. */
+		}
+
+		if (!ctx->match_parents)
+			break;
+
+		/* see if parent matches */
+		p = strrchr(name, mail_namespace_get_sep(ns));
+		if (p == NULL)
+			break;
+
+		name = t_strdup_until(name, p);
+		create_flags |= MAILBOX_NONEXISTENT;
+		create_flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+		always_flags = MAILBOX_CHILDREN | ctx->parent_flags;
+	}
+}
+
+void mailbox_list_iter_update(struct mailbox_list_iter_update_context *ctx,
+			      const char *name)
+{
+	T_BEGIN {
+		mailbox_list_iter_update_real(ctx, name);
+	} T_END;
+}
diff --git a/src/lib-storage/list/mailbox-list-maildir-iter.c b/src/lib-storage/list/mailbox-list-maildir-iter.c
new file mode 100644
index 0000000..df5fdd7
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-maildir-iter.c
@@ -0,0 +1,524 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "str.h"
+#include "ioloop.h"
+#include "unlink-directory.h"
+#include "unichar.h"
+#include "imap-match.h"
+#include "imap-utf7.h"
+#include "mailbox-tree.h"
+#include "mailbox-list-delete.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-maildir.h"
+
+#include <stdio.h>
+#include <dirent.h>
+#include <sys/stat.h>
+
+struct maildir_list_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+
+	const char *dir;
+	char prefix_char;
+
+        struct mailbox_tree_context *tree_ctx;
+	struct mailbox_tree_iterate_context *tree_iter;
+
+	struct mailbox_info info;
+};
+
+static void node_fix_parents(struct mailbox_node *node)
+{
+	/* Fix parent nodes' children states. also if we happened to create any
+	   of the parents, we need to mark them nonexistent. */
+	node = node->parent;
+	for (; node != NULL; node = node->parent) {
+		if ((node->flags & MAILBOX_MATCHED) == 0)
+			node->flags |= MAILBOX_NONEXISTENT;
+
+		node->flags |= MAILBOX_CHILDREN;
+		node->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+	}
+}
+
+static void
+maildir_fill_parents(struct maildir_list_iterate_context *ctx,
+		     struct imap_match_glob *glob, bool update_only,
+		     const char *vname)
+{
+	struct mail_namespace *ns = ctx->ctx.list->ns;
+	struct mailbox_node *node;
+	const char *p;
+	size_t vname_len = strlen(vname);
+	bool created;
+	char ns_sep = mail_namespace_get_sep(ns);
+
+	while ((p = strrchr(vname, ns_sep)) != NULL) {
+		vname = t_strdup_until(vname, p);
+		if (imap_match(glob, vname) != IMAP_MATCH_YES)
+			continue;
+
+		if (ns->prefix_len > 0 && vname_len == ns->prefix_len-1 &&
+		    strncmp(vname, ns->prefix, ns->prefix_len - 1) == 0 &&
+		    vname[ns->prefix_len-1] == ns_sep) {
+			/* don't return matches to namespace prefix itself */
+			continue;
+		}
+
+		created = FALSE;
+		node = update_only ?
+			mailbox_tree_lookup(ctx->tree_ctx, vname) :
+			mailbox_tree_get(ctx->tree_ctx, vname, &created);
+		if (node != NULL) {
+			if (created) {
+				/* we haven't yet seen this mailbox,
+				   but we might see it later */
+				node->flags = MAILBOX_NONEXISTENT;
+			}
+			if (!update_only)
+				node->flags |= MAILBOX_MATCHED;
+			node->flags |= MAILBOX_CHILDREN;
+			node->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+			node_fix_parents(node);
+		}
+	}
+}
+
+static void maildir_set_children(struct maildir_list_iterate_context *ctx,
+				 const char *vname)
+{
+	struct mailbox_node *node;
+	const char *p;
+	char hierarchy_sep;
+
+	hierarchy_sep = mail_namespace_get_sep(ctx->ctx.list->ns);
+
+	/* mark the first existing parent as containing children */
+	while ((p = strrchr(vname, hierarchy_sep)) != NULL) {
+		vname = t_strdup_until(vname, p);
+
+		node = mailbox_tree_lookup(ctx->tree_ctx, vname);
+		if (node != NULL) {
+			node->flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+			node->flags |= MAILBOX_CHILDREN;
+			break;
+		}
+	}
+}
+
+static int
+maildir_fill_inbox(struct maildir_list_iterate_context *ctx,
+		   struct imap_match_glob *glob, const char *inbox_name,
+		   bool update_only)
+{
+	struct mailbox_node *node;
+	enum mailbox_info_flags flags;
+	enum imap_match_result match;
+	bool created;
+	int ret;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_NO_AUTO_BOXES) == 0) {
+		/* always show INBOX */
+	} else {
+		/* INBOX may be Maildir root or completely elsewhere.
+		   show it only if it has already been created */
+		ret = mailbox_list_mailbox(ctx->ctx.list, "INBOX", &flags);
+		if (ret < 0)
+			return -1;
+		if ((flags & MAILBOX_NONEXISTENT) != 0)
+			update_only = TRUE;
+	}
+
+	if (update_only) {
+		node = mailbox_tree_lookup(ctx->tree_ctx, inbox_name);
+		if (node != NULL)
+			node->flags &= ENUM_NEGATE(MAILBOX_NONEXISTENT);
+		return 0;
+	}
+
+	/* add the INBOX only if it matches the patterns */
+	match = imap_match(glob, inbox_name);
+	if (match == IMAP_MATCH_PARENT)
+		maildir_fill_parents(ctx, glob, FALSE, inbox_name);
+	else if (match == IMAP_MATCH_YES) {
+		node = mailbox_tree_get(ctx->tree_ctx, inbox_name, &created);
+		if (created)
+			node->flags = MAILBOX_NOCHILDREN;
+		else
+			node->flags &= ENUM_NEGATE(MAILBOX_NONEXISTENT);
+		node->flags |= MAILBOX_MATCHED;
+	}
+	return 0;
+}
+
+static bool
+maildir_get_type(const char *dir, const char *fname,
+		 enum mailbox_list_file_type *type_r,
+		 enum mailbox_info_flags *flags)
+{
+	const char *path;
+	struct stat st;
+
+	path = *fname == '\0' ? dir :
+		t_strdup_printf("%s/%s", dir, fname);
+	if (stat(path, &st) < 0) {
+		if (errno == ENOENT) {
+			/* just deleted? */
+			*flags |= MAILBOX_NONEXISTENT;
+		} else {
+			*flags |= MAILBOX_NOSELECT;
+		}
+		return FALSE;
+	}
+
+	if (S_ISDIR(st.st_mode)) {
+		*type_r = MAILBOX_LIST_FILE_TYPE_DIR;
+		return TRUE;
+	} else {
+		if (str_begins(fname, ".nfs"))
+			*flags |= MAILBOX_NONEXISTENT;
+		else
+			*flags |= MAILBOX_NOSELECT;
+		return FALSE;
+	}
+}
+
+int maildir_list_get_mailbox_flags(struct mailbox_list *list,
+				   const char *dir, const char *fname,
+				   enum mailbox_list_file_type type,
+				   enum mailbox_info_flags *flags_r)
+{
+	*flags_r = 0;
+
+	switch (type) {
+	case MAILBOX_LIST_FILE_TYPE_DIR:
+	case MAILBOX_LIST_FILE_TYPE_FILE:
+	case MAILBOX_LIST_FILE_TYPE_OTHER:
+		break;
+	case MAILBOX_LIST_FILE_TYPE_UNKNOWN:
+	case MAILBOX_LIST_FILE_TYPE_SYMLINK:
+		/* need to check with stat() to be sure */
+		if (!list->mail_set->maildir_stat_dirs && *fname != '\0' &&
+		    strcmp(list->name, MAILBOX_LIST_NAME_MAILDIRPLUSPLUS) == 0 &&
+		    !str_begins(fname, ".nfs")) {
+			/* just assume it's a valid mailbox */
+			return 1;
+		}
+
+		if (!maildir_get_type(dir, fname, &type, flags_r))
+			return 0;
+		break;
+	}
+
+	switch (type) {
+	case MAILBOX_LIST_FILE_TYPE_DIR:
+		if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+			*flags_r |= MAILBOX_NOSELECT;
+			return 0;
+		}
+		break;
+	case MAILBOX_LIST_FILE_TYPE_FILE:
+		if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) == 0) {
+			*flags_r |= MAILBOX_NOSELECT;
+			return 0;
+		}
+		break;
+	case MAILBOX_LIST_FILE_TYPE_OTHER:
+		*flags_r |= MAILBOX_NOSELECT;
+		return 0;
+
+	case MAILBOX_LIST_FILE_TYPE_UNKNOWN:
+	case MAILBOX_LIST_FILE_TYPE_SYMLINK:
+		i_unreached();
+	}
+	if (*fname != '\0') {
+		/* this tells maildir storage code that it doesn't need to
+		   see if cur/ exists, because just the existence of .dir/
+		   assumes that the mailbox exists. */
+		*flags_r |= MAILBOX_SELECT;
+	}
+	return 1;
+}
+
+static bool maildir_delete_trash_dir(struct maildir_list_iterate_context *ctx,
+				     const char *fname)
+{
+	const char *path, *error;
+	struct stat st;
+
+	if (fname[1] != ctx->prefix_char || ctx->prefix_char == '\0' ||
+	    strcmp(fname+2, MAILBOX_LIST_MAILDIR_TRASH_DIR_NAME) != 0)
+		return FALSE;
+
+	/* this directory is in the middle of being deleted, or the process
+	   trying to delete it had died. delete it ourself if it's been there
+	   longer than one hour. */
+	path = t_strdup_printf("%s/%s", ctx->dir, fname);
+	if (stat(path, &st) == 0 &&
+	    st.st_mtime < ioloop_time - 3600)
+		(void)mailbox_list_delete_trash(path, &error);
+
+	return TRUE;
+}
+
+static int
+maildir_fill_readdir_entry(struct maildir_list_iterate_context *ctx,
+			   struct imap_match_glob *glob, const struct dirent *d,
+			   bool update_only)
+{
+	struct mailbox_list *list = ctx->ctx.list;
+	const char *fname, *storage_name, *vname;
+	enum mailbox_info_flags flags;
+	enum imap_match_result match;
+	struct mailbox_node *node;
+	bool created;
+	int ret;
+
+	fname = d->d_name;
+	if (fname[0] == ctx->prefix_char)
+		storage_name = fname + 1;
+	else {
+		if (ctx->prefix_char != '\0' || fname[0] == '.')
+			return 0;
+		storage_name = fname;
+	}
+
+	/* skip . and .. */
+	if (fname[0] == '.' &&
+	    (fname[1] == '\0' || (fname[1] == '.' && fname[2] == '\0')))
+		return 0;
+
+	vname = mailbox_list_get_vname(list, storage_name);
+	if (!uni_utf8_str_is_valid(vname)) {
+		/* the storage_name is completely invalid, rename it to
+		   something more sensible. we could do this for all names that
+		   aren't valid mUTF-7, but that might lead to accidents in
+		   future when UTF-8 storage names are used */
+		const char *src = t_strdup_printf("%s/%s", ctx->dir, fname);
+		string_t *destvname = t_str_new(128);
+		string_t *dest = t_str_new(128);
+
+		if (uni_utf8_get_valid_data((const void *)fname,
+					    strlen(fname), destvname))
+			i_unreached(); /* already checked that it was invalid */
+
+		str_append(dest, ctx->dir);
+		str_append_c(dest, '/');
+		(void)imap_utf8_to_utf7(str_c(destvname), dest);
+
+		if (rename(src, str_c(dest)) < 0 && errno != ENOENT)
+			e_error(ctx->ctx.list->ns->user->event,
+				"rename(%s, %s) failed: %m", src, str_c(dest));
+		/* just skip this in this iteration, we'll see it on the
+		   next list */
+		return 0;
+	}
+
+	/* make sure the pattern matches */
+	match = imap_match(glob, vname);
+	if ((match & (IMAP_MATCH_YES | IMAP_MATCH_PARENT)) == 0)
+		return 0;
+
+	/* check if this is an actual mailbox */
+	if (maildir_delete_trash_dir(ctx, fname))
+		return 0;
+
+	if ((ctx->ctx.flags & MAILBOX_LIST_ITER_SKIP_ALIASES) != 0) {
+		ret = mailbox_list_dirent_is_alias_symlink(list, ctx->dir, d);
+		if (ret != 0)
+			return ret < 0 ? -1 : 0;
+	}
+	T_BEGIN {
+		ret = list->v.get_mailbox_flags(list, ctx->dir, fname,
+				mailbox_list_get_file_type(d), &flags);
+	} T_END;
+	if (ret <= 0)
+		return ret;
+
+	/* we know the children flags ourself, so ignore if any of
+	   them were set. */
+	flags &= ENUM_NEGATE(MAILBOX_NOINFERIORS | MAILBOX_CHILDREN | MAILBOX_NOCHILDREN);
+
+	if ((match & IMAP_MATCH_PARENT) != 0)
+		maildir_fill_parents(ctx, glob, update_only, vname);
+	else {
+		created = FALSE;
+		node = update_only ?
+			mailbox_tree_lookup(ctx->tree_ctx, vname) :
+			mailbox_tree_get(ctx->tree_ctx, vname, &created);
+
+		if (node != NULL) {
+			if (created)
+				node->flags = MAILBOX_NOCHILDREN;
+			else
+				node->flags &= ENUM_NEGATE(MAILBOX_NONEXISTENT);
+			if (!update_only)
+				node->flags |= MAILBOX_MATCHED;
+			node->flags |= flags;
+			node_fix_parents(node);
+		} else {
+			i_assert(update_only);
+			maildir_set_children(ctx, vname);
+		}
+	}
+	return 0;
+}
+
+static int
+maildir_fill_readdir(struct maildir_list_iterate_context *ctx,
+		     struct imap_match_glob *glob, bool update_only)
+{
+	struct mailbox_list *list = ctx->ctx.list;
+	struct mail_namespace *ns = list->ns;
+	DIR *dirp;
+	struct dirent *d;
+	const char *vname;
+	int ret = 0;
+
+	dirp = opendir(ctx->dir);
+	if (dirp == NULL) {
+		if (errno == EACCES) {
+			mailbox_list_set_critical(list, "%s",
+				mail_error_eacces_msg("opendir", ctx->dir));
+		} else if (errno != ENOENT) {
+			mailbox_list_set_critical(list,
+				"opendir(%s) failed: %m", ctx->dir);
+			return -1;
+		}
+		return 0;
+	}
+
+	while ((d = readdir(dirp)) != NULL) {
+		T_BEGIN {
+			ret = maildir_fill_readdir_entry(ctx, glob, d,
+							 update_only);
+		} T_END;
+		if (ret < 0)
+			break;
+	}
+
+	if (closedir(dirp) < 0) {
+		mailbox_list_set_critical(list, "readdir(%s) failed: %m",
+					  ctx->dir);
+		return -1;
+	}
+	if (ret < 0)
+		return -1;
+
+	if ((ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0) {
+		/* make sure INBOX is listed */
+		return maildir_fill_inbox(ctx, glob, "INBOX", update_only);
+	} else if ((ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0) {
+		/* show shared INBOX. */
+		vname = mailbox_list_get_vname(ns->list, "INBOX");
+		return maildir_fill_inbox(ctx, glob, vname, update_only);
+	} else {
+		return 0;
+	}
+}
+
+struct mailbox_list_iterate_context *
+maildir_list_iter_init(struct mailbox_list *_list, const char *const *patterns,
+		       enum mailbox_list_iter_flags flags)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+	struct maildir_list_iterate_context *ctx;
+	pool_t pool;
+	char ns_sep = mail_namespace_get_sep(_list->ns);
+	int ret;
+
+	pool = pool_alloconly_create("mailbox list maildir iter", 1024);
+	ctx = p_new(pool, struct maildir_list_iterate_context, 1);
+	ctx->ctx.pool = pool;
+	ctx->ctx.list = _list;
+	ctx->ctx.flags = flags;
+	ctx->ctx.glob = imap_match_init_multiple(pool, patterns, TRUE, ns_sep);
+	array_create(&ctx->ctx.module_contexts, pool, sizeof(void *), 5);
+
+	ctx->tree_ctx = mailbox_tree_init(ns_sep);
+	ctx->info.ns = _list->ns;
+	ctx->prefix_char = strcmp(_list->name, MAILBOX_LIST_NAME_IMAPDIR) == 0 ?
+		'\0' : list->sep;
+
+	if (_list->set.iter_from_index_dir)
+		ctx->dir = _list->set.index_dir;
+	else
+		ctx->dir = _list->set.root_dir;
+
+	if ((flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0) {
+		/* Listing only subscribed mailboxes.
+		   Flags are set later if needed. */
+		bool default_nonexistent =
+			(flags & MAILBOX_LIST_ITER_RETURN_NO_FLAGS) == 0;
+
+		mailbox_list_subscriptions_fill(&ctx->ctx, ctx->tree_ctx,
+						default_nonexistent);
+	}
+
+	if ((flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0 ||
+	    (flags & MAILBOX_LIST_ITER_RETURN_NO_FLAGS) == 0) {
+		/* Add/update mailbox list with flags */
+		bool update_only =
+			(flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) != 0;
+
+		T_BEGIN {
+			ret = maildir_fill_readdir(ctx, ctx->ctx.glob,
+						   update_only);
+		} T_END;
+		if (ret < 0) {
+			ctx->ctx.failed = TRUE;
+			return &ctx->ctx;
+		}
+	}
+
+	ctx->tree_iter = mailbox_tree_iterate_init(ctx->tree_ctx, NULL,
+						   MAILBOX_MATCHED);
+	return &ctx->ctx;
+}
+
+int maildir_list_iter_deinit(struct mailbox_list_iterate_context *_ctx)
+{
+	struct maildir_list_iterate_context *ctx =
+		(struct maildir_list_iterate_context *)_ctx;
+	int ret = _ctx->failed ? -1 : 0;
+
+	if (ctx->tree_iter != NULL)
+		mailbox_tree_iterate_deinit(&ctx->tree_iter);
+	mailbox_tree_deinit(&ctx->tree_ctx);
+	pool_unref(&ctx->ctx.pool);
+	return ret;
+}
+
+const struct mailbox_info *
+maildir_list_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	struct maildir_list_iterate_context *ctx =
+		(struct maildir_list_iterate_context *)_ctx;
+	struct mailbox_node *node;
+
+	if (_ctx->failed)
+		return NULL;
+
+	node = mailbox_tree_iterate_next(ctx->tree_iter, &ctx->info.vname);
+	if (node == NULL)
+		return mailbox_list_iter_default_next(_ctx);
+
+	ctx->info.flags = node->flags;
+	if (strcmp(ctx->info.vname, "INBOX") == 0 &&
+	    mail_namespace_is_inbox_noinferiors(ctx->info.ns)) {
+		i_assert((ctx->info.flags & MAILBOX_NOCHILDREN) != 0);
+		ctx->info.flags &= ENUM_NEGATE(MAILBOX_NOCHILDREN);
+		ctx->info.flags |= MAILBOX_NOINFERIORS;
+	}
+	if ((_ctx->flags & MAILBOX_LIST_ITER_RETURN_SUBSCRIBED) != 0 &&
+	    (_ctx->flags & MAILBOX_LIST_ITER_SELECT_SUBSCRIBED) == 0) {
+		/* we're listing all mailboxes but we want to know
+		   \Subscribed flags */
+		mailbox_list_set_subscription_flags(_ctx->list, ctx->info.vname,
+						    &ctx->info.flags);
+	}
+	return &ctx->info;
+}
diff --git a/src/lib-storage/list/mailbox-list-maildir.c b/src/lib-storage/list/mailbox-list-maildir.c
new file mode 100644
index 0000000..265f3d0
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-maildir.c
@@ -0,0 +1,546 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "hostpid.h"
+#include "eacces-error.h"
+#include "mkdir-parents.h"
+#include "str.h"
+#include "subscription-file.h"
+#include "mailbox-list-subscriptions.h"
+#include "mailbox-list-delete.h"
+#include "mailbox-list-maildir.h"
+
+#include <stdio.h>
+#include <sys/stat.h>
+
+#define MAILDIR_GLOBAL_TEMP_PREFIX "temp."
+#define IMAPDIR_GLOBAL_TEMP_PREFIX ".temp."
+
+extern struct mailbox_list maildir_mailbox_list;
+extern struct mailbox_list imapdir_mailbox_list;
+
+static struct mailbox_list *maildir_list_alloc(void)
+{
+	struct maildir_mailbox_list *list;
+	pool_t pool;
+
+	pool = pool_alloconly_create("maildir++ list", 2048);
+	list = p_new(pool, struct maildir_mailbox_list, 1);
+	list->list = maildir_mailbox_list;
+	list->list.pool = pool;
+	list->sep = '.';
+
+	list->global_temp_prefix = MAILDIR_GLOBAL_TEMP_PREFIX;
+	list->temp_prefix = p_strconcat(pool, list->global_temp_prefix,
+					my_hostname, ".", my_pid, ".", NULL);
+	return &list->list;
+}
+
+static struct mailbox_list *imapdir_list_alloc(void)
+{
+	struct maildir_mailbox_list *list;
+	pool_t pool;
+
+	pool = pool_alloconly_create("imapdir list", 1024);
+	list = p_new(pool, struct maildir_mailbox_list, 1);
+	list->list = imapdir_mailbox_list;
+	list->list.pool = pool;
+	list->sep = '.';
+
+	list->global_temp_prefix = IMAPDIR_GLOBAL_TEMP_PREFIX;
+	list->temp_prefix = p_strconcat(pool, list->global_temp_prefix,
+					my_hostname, ".", my_pid, ".", NULL);
+	return &list->list;
+}
+
+static void maildir_list_deinit(struct mailbox_list *_list)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+
+	pool_unref(&list->list.pool);
+}
+
+static const char *
+maildir_list_get_dirname_path(struct mailbox_list *list, const char *dir,
+			      const char *name)
+{
+	if (*name == '\0')
+		return dir;
+	else if (strcmp(list->name, imapdir_mailbox_list.name) == 0)
+		return t_strdup_printf("%s/%s", dir, name);
+
+	return t_strdup_printf("%s/%c%s", dir,
+			       mailbox_list_get_hierarchy_sep(list), name);
+}
+
+static const char *
+maildir_list_get_absolute_path(struct mailbox_list *list, const char *name)
+{
+	const char *p;
+
+	if (!mailbox_list_try_get_absolute_path(list, &name)) {
+		/* fallback to using as ~name */
+		return name;
+	}
+
+	p = strrchr(name, '/');
+	if (p == NULL)
+		return name;
+	return maildir_list_get_dirname_path(list, t_strdup_until(name, p),
+					     p+1);
+}
+
+static char maildir_list_get_hierarchy_sep(struct mailbox_list *_list)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+
+	return list->sep;
+}
+
+static int
+maildir_list_get_path(struct mailbox_list *_list, const char *name,
+		      enum mailbox_list_path_type type, const char **path_r)
+{
+	const char *root_dir;
+
+	if (name == NULL) {
+		/* return root directories */
+		return mailbox_list_set_get_root_path(&_list->set, type,
+						      path_r) ? 1 : 0;
+	}
+
+	if (_list->mail_set->mail_full_filesystem_access &&
+	    (*name == '/' || *name == '~')) {
+		*path_r = maildir_list_get_absolute_path(_list, name);
+		return 1;
+	}
+
+	root_dir = _list->set.root_dir;
+	switch (type) {
+	case MAILBOX_LIST_PATH_TYPE_DIR:
+	case MAILBOX_LIST_PATH_TYPE_MAILBOX:
+		break;
+	case MAILBOX_LIST_PATH_TYPE_ALT_DIR:
+	case MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX:
+		if (_list->set.alt_dir == NULL)
+			return 0;
+		root_dir = _list->set.alt_dir;
+		break;
+	case MAILBOX_LIST_PATH_TYPE_CONTROL:
+		if (_list->set.control_dir != NULL) {
+			*path_r = maildir_list_get_dirname_path(_list,
+					       _list->set.control_dir, name);
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_PATH_TYPE_INDEX_CACHE:
+		if (_list->set.index_cache_dir != NULL) {
+			*path_r = maildir_list_get_dirname_path(_list,
+						_list->set.index_cache_dir, name);
+			return 1;
+		}
+		/* fall through */
+	case MAILBOX_LIST_PATH_TYPE_INDEX:
+		if (_list->set.index_dir != NULL) {
+			if (*_list->set.index_dir == '\0')
+				return 0;
+			*path_r = maildir_list_get_dirname_path(_list,
+						_list->set.index_dir, name);
+			return 1;
+		}
+		break;
+	case MAILBOX_LIST_PATH_TYPE_INDEX_PRIVATE:
+		if (_list->set.index_pvt_dir == NULL)
+			return 0;
+		*path_r = maildir_list_get_dirname_path(_list,
+					_list->set.index_pvt_dir, name);
+		return 1;
+	case MAILBOX_LIST_PATH_TYPE_LIST_INDEX:
+		i_unreached();
+	}
+
+	if (type == MAILBOX_LIST_PATH_TYPE_ALT_DIR ||
+	    type == MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX) {
+		/* don't use inbox_path */
+	} else if (strcmp(name, "INBOX") == 0 && _list->set.inbox_path != NULL) {
+		*path_r = _list->set.inbox_path;
+		return 1;
+	}
+
+	*path_r = maildir_list_get_dirname_path(_list, root_dir, name);
+	return 1;
+}
+
+static const char *
+maildir_list_get_temp_prefix(struct mailbox_list *_list, bool global)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+
+	return global ? list->global_temp_prefix : list->temp_prefix;
+}
+
+static int maildir_list_set_subscribed(struct mailbox_list *_list,
+				       const char *name, bool set)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+	const char *path;
+
+	if (_list->set.subscription_fname == NULL) {
+		mailbox_list_set_error(_list, MAIL_ERROR_NOTPOSSIBLE,
+				       "Subscriptions not supported");
+		return -1;
+	}
+
+	path = t_strconcat(_list->set.control_dir != NULL ?
+			   _list->set.control_dir : _list->set.root_dir,
+			   "/", _list->set.subscription_fname, NULL);
+
+	return subsfile_set_subscribed(_list, path, list->temp_prefix,
+				       name, set);
+}
+
+static const char *
+mailbox_list_maildir_get_trash_dir(struct mailbox_list *_list)
+{
+	struct maildir_mailbox_list *list =
+		(struct maildir_mailbox_list *)_list;
+	const char *root_dir;
+
+	root_dir = mailbox_list_get_root_forced(_list, MAILBOX_LIST_PATH_TYPE_DIR);
+	return t_strdup_printf("%s/%c%c"MAILBOX_LIST_MAILDIR_TRASH_DIR_NAME,
+			       root_dir, list->sep, list->sep);
+}
+
+static int
+maildir_list_delete_maildir(struct mailbox_list *list, const char *name)
+{
+	const char *path, *trash_dir;
+	int ret = 0;
+
+	trash_dir = mailbox_list_maildir_get_trash_dir(list);
+	ret = mailbox_list_delete_maildir_via_trash(list, name, trash_dir);
+	if (ret < 0)
+		return -1;
+
+	if (ret == 0) {
+		/* we could actually use just unlink_directory()
+		   but error handling is easier this way :) */
+		if (mailbox_list_get_path(list, name,
+					  MAILBOX_LIST_PATH_TYPE_MAILBOX,
+					  &path) <= 0)
+			i_unreached();
+		if (mailbox_list_delete_mailbox_nonrecursive(list, name,
+							     path, TRUE) < 0)
+			return -1;
+	}
+	return 0;
+}
+
+static int
+maildir_list_delete_mailbox(struct mailbox_list *list, const char *name)
+{
+	const char *path;
+	int ret;
+
+	if ((list->flags & MAILBOX_LIST_FLAG_MAILBOX_FILES) != 0) {
+		ret = mailbox_list_get_path(list, name,
+					    MAILBOX_LIST_PATH_TYPE_MAILBOX,
+					    &path);
+		if (ret < 0)
+			return -1;
+		i_assert(ret > 0);
+		ret = mailbox_list_delete_mailbox_file(list, name, path);
+	} else {
+		ret = maildir_list_delete_maildir(list, name);
+	}
+
+	i_assert(ret <= 0);
+	return mailbox_list_delete_finish_ret(list, name, ret == 0);
+}
+
+static int maildir_list_delete_dir(struct mailbox_list *list, const char *name)
+{
+	const char *path;
+	struct stat st;
+
+	/* with maildir++ there aren't any non-selectable mailboxes.
+	   we'll always fail. */
+	if (mailbox_list_get_path(list, name, MAILBOX_LIST_PATH_TYPE_DIR,
+				  &path) <= 0)
+		i_unreached();
+	if (stat(path, &st) == 0) {
+		mailbox_list_set_error(list, MAIL_ERROR_EXISTS,
+				       "Mailbox exists");
+	} else if (errno == ENOENT || errno == ENOTDIR) {
+		mailbox_list_set_error(list, MAIL_ERROR_NOTFOUND,
+			T_MAILBOX_LIST_ERR_NOT_FOUND(list, name));
+	} else {
+		mailbox_list_set_critical(list, "stat(%s) failed: %m", path);
+	}
+	return -1;
+}
+
+static int rename_dir(struct mailbox_list *oldlist, const char *oldname,
+		      struct mailbox_list *newlist, const char *newname,
+		      enum mailbox_list_path_type type)
+{
+	const char *oldpath, *newpath;
+
+	if (mailbox_list_get_path(oldlist, oldname, type, &oldpath) <= 0 ||
+	    mailbox_list_get_path(newlist, newname, type, &newpath) <= 0)
+		return 0;
+
+	if (strcmp(oldpath, newpath) == 0)
+		return 0;
+
+	if (rename(oldpath, newpath) < 0 && errno != ENOENT) {
+		mailbox_list_set_critical(oldlist, "rename(%s, %s) failed: %m",
+					  oldpath, newpath);
+		return -1;
+	}
+	return 0;
+}
+
+static int
+maildir_rename_children(struct mailbox_list *oldlist, const char *oldname,
+			struct mailbox_list *newlist, const char *newname)
+{
+	struct mailbox_list_iterate_context *iter;
+        const struct mailbox_info *info;
+	ARRAY(const char *) names_arr;
+	const char *pattern, *oldpath, *newpath, *old_childname, *new_childname;
+	const char *const *names, *old_vname, *new_vname;
+	unsigned int i, count;
+	size_t old_vnamelen;
+	pool_t pool;
+	char old_ns_sep;
+	int ret;
+
+	ret = 0;
+
+	/* first get the list of the children and save them to memory, because
+	   we can't rely on readdir() not skipping files while the directory
+	   is being modified. this doesn't protect against modifications by
+	   other processes though. */
+	pool = pool_alloconly_create("Maildir++ children list", 1024);
+	i_array_init(&names_arr, 64);
+
+	old_vname = mailbox_list_get_vname(oldlist, oldname);
+	old_vnamelen = strlen(old_vname);
+
+	new_vname = mailbox_list_get_vname(newlist, newname);
+
+	old_ns_sep = mail_namespace_get_sep(oldlist->ns);
+	pattern = t_strdup_printf("%s%c*", old_vname, old_ns_sep);
+	iter = mailbox_list_iter_init(oldlist, pattern,
+				      MAILBOX_LIST_ITER_RETURN_NO_FLAGS |
+				      MAILBOX_LIST_ITER_RAW_LIST);
+	while ((info = mailbox_list_iter_next(iter)) != NULL) {
+		const char *name;
+
+		/* verify that the prefix matches, otherwise we could have
+		   problems with mailbox names containing '%' and '*' chars */
+		if (strncmp(info->vname, old_vname, old_vnamelen) == 0 &&
+		    info->vname[old_vnamelen] == old_ns_sep) {
+			name = p_strdup(pool, info->vname + old_vnamelen);
+			array_push_back(&names_arr, &name);
+		}
+	}
+	if (mailbox_list_iter_deinit(&iter) < 0) {
+		ret = -1;
+		names = NULL; count = 0;
+	} else {
+		names = array_get(&names_arr, &count);
+	}
+
+	for (i = 0; i < count; i++) {
+		old_childname = mailbox_list_get_storage_name(oldlist,
+					t_strconcat(old_vname, names[i], NULL));
+		if (strcmp(old_childname, new_vname) == 0) {
+			/* When doing RENAME "a" "a.b" we see "a.b" here.
+			   We don't want to rename it anymore to "a.b.b". */
+			continue;
+		}
+
+		new_childname = mailbox_list_get_storage_name(newlist,
+					t_strconcat(new_vname, names[i], NULL));
+		if (mailbox_list_get_path(oldlist, old_childname,
+					  MAILBOX_LIST_PATH_TYPE_MAILBOX,
+					  &oldpath) <= 0 ||
+		    mailbox_list_get_path(newlist, new_childname,
+					  MAILBOX_LIST_PATH_TYPE_MAILBOX,
+					  &newpath) <= 0)
+			i_unreached();
+
+		/* FIXME: it's possible to merge two mailboxes if either one of
+		   them doesn't have existing root mailbox. We could check this
+		   but I'm not sure if it's worth it. It could be even
+		   considered as a feature.
+
+		   Anyway, the bug with merging is that if both mailboxes have
+		   identically named child mailbox they conflict. Just ignore
+		   those and leave them under the old mailbox. */
+		if (rename(oldpath, newpath) == 0 || EDESTDIREXISTS(errno))
+			ret = 1;
+		else {
+			mailbox_list_set_critical(oldlist,
+				"rename(%s, %s) failed: %m", oldpath, newpath);
+			ret = -1;
+			break;
+		}
+
+		(void)rename_dir(oldlist, old_childname, newlist, new_childname,
+				 MAILBOX_LIST_PATH_TYPE_CONTROL);
+		(void)rename_dir(oldlist, old_childname, newlist, new_childname,
+				 MAILBOX_LIST_PATH_TYPE_INDEX);
+		(void)rename_dir(oldlist, old_childname, newlist, new_childname,
+				 MAILBOX_LIST_PATH_TYPE_INDEX_CACHE);
+	}
+	array_free(&names_arr);
+	pool_unref(&pool);
+
+	return ret;
+}
+
+static int
+maildir_list_rename_mailbox(struct mailbox_list *oldlist, const char *oldname,
+			    struct mailbox_list *newlist, const char *newname)
+{
+	const char *oldpath, *newpath, *root_path;
+	int ret;
+        bool found;
+
+	/* NOTE: it's possible to rename a nonexistent mailbox which has
+	   children. In that case we should ignore the rename() error. */
+	if (mailbox_list_get_path(oldlist, oldname,
+				  MAILBOX_LIST_PATH_TYPE_MAILBOX, &oldpath) <= 0 ||
+	    mailbox_list_get_path(newlist, newname,
+				  MAILBOX_LIST_PATH_TYPE_MAILBOX, &newpath) <= 0)
+		i_unreached();
+
+	root_path = mailbox_list_get_root_forced(oldlist,
+						 MAILBOX_LIST_PATH_TYPE_MAILBOX);
+	if (strcmp(oldpath, root_path) == 0) {
+		/* most likely INBOX */
+		mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			t_strdup_printf("Renaming %s isn't supported.",
+					oldname));
+		return -1;
+	}
+
+	/* if we're renaming under another mailbox, require its permissions
+	   to be same as ours. */
+	if (strchr(newname, mailbox_list_get_hierarchy_sep(newlist)) != NULL) {
+		struct mailbox_permissions old_perm, new_perm;
+
+		mailbox_list_get_permissions(oldlist, oldname, &old_perm);
+		mailbox_list_get_permissions(newlist, newname, &new_perm);
+
+		if ((new_perm.file_create_mode != old_perm.file_create_mode ||
+		     new_perm.dir_create_mode != old_perm.dir_create_mode ||
+		     new_perm.file_create_gid != old_perm.file_create_gid)) {
+			mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+				"Renaming not supported across conflicting "
+				"directory permissions");
+			return -1;
+		}
+	}
+
+
+	ret = rename(oldpath, newpath);
+	if (ret == 0 || errno == ENOENT) {
+		(void)rename_dir(oldlist, oldname, newlist, newname,
+				 MAILBOX_LIST_PATH_TYPE_CONTROL);
+		(void)rename_dir(oldlist, oldname, newlist, newname,
+				 MAILBOX_LIST_PATH_TYPE_INDEX);
+		(void)rename_dir(oldlist, oldname, newlist, newname,
+				 MAILBOX_LIST_PATH_TYPE_INDEX_CACHE);
+
+		found = ret == 0;
+		T_BEGIN {
+			ret = maildir_rename_children(oldlist, oldname,
+						      newlist, newname);
+		} T_END;
+		if (ret < 0)
+			return -1;
+		if (!found && ret == 0) {
+			mailbox_list_set_error(oldlist, MAIL_ERROR_NOTFOUND,
+				T_MAILBOX_LIST_ERR_NOT_FOUND(oldlist, oldname));
+			return -1;
+		}
+
+		return 0;
+	}
+
+	if (EDESTDIREXISTS(errno)) {
+		mailbox_list_set_error(oldlist, MAIL_ERROR_EXISTS,
+				       "Target mailbox already exists");
+	} else {
+		mailbox_list_set_critical(oldlist, "rename(%s, %s) failed: %m",
+					  oldpath, newpath);
+	}
+	return -1;
+}
+
+struct mailbox_list maildir_mailbox_list = {
+	.name = MAILBOX_LIST_NAME_MAILDIRPLUSPLUS,
+	.props = MAILBOX_LIST_PROP_NO_MAILDIR_NAME |
+		MAILBOX_LIST_PROP_NO_ALT_DIR |
+		MAILBOX_LIST_PROP_NO_NOSELECT |
+		MAILBOX_LIST_PROP_NO_INTERNAL_NAMES,
+	.mailbox_name_max_length = MAILBOX_LIST_NAME_MAX_LENGTH,
+
+	.v = {
+		.alloc = maildir_list_alloc,
+		.deinit = maildir_list_deinit,
+		.get_hierarchy_sep = maildir_list_get_hierarchy_sep,
+		.get_vname = mailbox_list_default_get_vname,
+		.get_storage_name = mailbox_list_default_get_storage_name,
+		.get_path = maildir_list_get_path,
+		.get_temp_prefix = maildir_list_get_temp_prefix,
+		.iter_init = maildir_list_iter_init,
+		.iter_next = maildir_list_iter_next,
+		.iter_deinit = maildir_list_iter_deinit,
+		.get_mailbox_flags = maildir_list_get_mailbox_flags,
+		.subscriptions_refresh = mailbox_list_subscriptions_refresh,
+		.set_subscribed = maildir_list_set_subscribed,
+		.delete_mailbox = maildir_list_delete_mailbox,
+		.delete_dir = maildir_list_delete_dir,
+		.delete_symlink = mailbox_list_delete_symlink_default,
+		.rename_mailbox = maildir_list_rename_mailbox,
+	}
+};
+
+struct mailbox_list imapdir_mailbox_list = {
+	.name = MAILBOX_LIST_NAME_IMAPDIR,
+	.props = MAILBOX_LIST_PROP_NO_MAILDIR_NAME |
+		MAILBOX_LIST_PROP_NO_ALT_DIR |
+		MAILBOX_LIST_PROP_NO_NOSELECT |
+		MAILBOX_LIST_PROP_NO_INTERNAL_NAMES,
+	.mailbox_name_max_length = MAILBOX_LIST_NAME_MAX_LENGTH,
+
+	.v = {
+		.alloc = imapdir_list_alloc,
+		.deinit = maildir_list_deinit,
+		.get_hierarchy_sep = maildir_list_get_hierarchy_sep,
+		.get_vname = mailbox_list_default_get_vname,
+		.get_storage_name = mailbox_list_default_get_storage_name,
+		.get_path = maildir_list_get_path,
+		.get_temp_prefix = maildir_list_get_temp_prefix,
+		.iter_init = maildir_list_iter_init,
+		.iter_next = maildir_list_iter_next,
+		.iter_deinit = maildir_list_iter_deinit,
+		.get_mailbox_flags = maildir_list_get_mailbox_flags,
+		.subscriptions_refresh = mailbox_list_subscriptions_refresh,
+		.set_subscribed = maildir_list_set_subscribed,
+		.delete_mailbox = maildir_list_delete_mailbox,
+		.delete_dir = maildir_list_delete_dir,
+		.delete_symlink = mailbox_list_delete_symlink_default,
+		.rename_mailbox = maildir_list_rename_mailbox,
+	}
+};
diff --git a/src/lib-storage/list/mailbox-list-maildir.h b/src/lib-storage/list/mailbox-list-maildir.h
new file mode 100644
index 0000000..3760378
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-maildir.h
@@ -0,0 +1,29 @@
+#ifndef MAILBOX_LIST_MAILDIR_H
+#define MAILBOX_LIST_MAILDIR_H
+
+#include "mailbox-list-private.h"
+
+/* When doing deletion via renaming it first to trash directory, use this as
+   the trash directory name */
+#define MAILBOX_LIST_MAILDIR_TRASH_DIR_NAME "DOVECOT-TRASHED"
+
+struct maildir_mailbox_list {
+	struct mailbox_list list;
+
+	const char *global_temp_prefix, *temp_prefix;
+	char sep;
+};
+
+struct mailbox_list_iterate_context *
+maildir_list_iter_init(struct mailbox_list *_list, const char *const *patterns,
+		       enum mailbox_list_iter_flags flags);
+int maildir_list_iter_deinit(struct mailbox_list_iterate_context *ctx);
+const struct mailbox_info *
+maildir_list_iter_next(struct mailbox_list_iterate_context *ctx);
+
+int maildir_list_get_mailbox_flags(struct mailbox_list *list,
+				   const char *dir, const char *fname,
+				   enum mailbox_list_file_type type,
+				   enum mailbox_info_flags *flags);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-none.c b/src/lib-storage/list/mailbox-list-none.c
new file mode 100644
index 0000000..fb5c608
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-none.c
@@ -0,0 +1,178 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "imap-match.h"
+#include "mailbox-list-private.h"
+
+#define GLOBAL_TEMP_PREFIX ".temp."
+
+struct noop_list_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+	struct mailbox_info inbox_info;
+	bool list_inbox:1;
+};
+
+extern struct mailbox_list none_mailbox_list;
+
+static struct mailbox_list *none_list_alloc(void)
+{
+	struct mailbox_list *list;
+	pool_t pool;
+
+	pool = pool_alloconly_create("none list", 2048);
+
+	list = p_new(pool, struct mailbox_list, 1);
+	*list = none_mailbox_list;
+	list->props = MAILBOX_LIST_PROP_NO_LIST_INDEX;
+	list->pool = pool;
+	return list;
+}
+
+static void none_list_deinit(struct mailbox_list *list)
+{
+	pool_unref(&list->pool);
+}
+
+static char none_list_get_hierarchy_sep(struct mailbox_list *list ATTR_UNUSED)
+{
+	return '/';
+}
+
+static int
+none_list_get_path(struct mailbox_list *list ATTR_UNUSED,
+		   const char *name ATTR_UNUSED,
+		   enum mailbox_list_path_type type ATTR_UNUSED,
+		   const char **path_r ATTR_UNUSED)
+{
+	return 0;
+}
+
+static const char *
+none_list_get_temp_prefix(struct mailbox_list *list ATTR_UNUSED,
+			  bool global ATTR_UNUSED)
+{
+	return GLOBAL_TEMP_PREFIX;
+}
+
+static int
+none_list_subscriptions_refresh(struct mailbox_list *src_list ATTR_UNUSED,
+				struct mailbox_list *dest_list ATTR_UNUSED)
+{
+	return 0;
+}
+
+static int none_list_set_subscribed(struct mailbox_list *list,
+				    const char *name ATTR_UNUSED,
+				    bool set ATTR_UNUSED)
+{
+	mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE, "Not supported");
+	return -1;
+}
+
+static int none_list_delete_mailbox(struct mailbox_list *list,
+				    const char *name ATTR_UNUSED)
+{
+	mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE, "Not supported");
+	return -1;
+}
+
+static int none_list_delete_dir(struct mailbox_list *list,
+				const char *name ATTR_UNUSED)
+{
+	mailbox_list_set_error(list, MAIL_ERROR_NOTPOSSIBLE, "Not supported");
+	return -1;
+}
+
+static int
+none_list_rename_mailbox(struct mailbox_list *oldlist,
+			 const char *oldname ATTR_UNUSED,
+			 struct mailbox_list *newlist ATTR_UNUSED,
+			 const char *newname ATTR_UNUSED)
+{
+	mailbox_list_set_error(oldlist, MAIL_ERROR_NOTPOSSIBLE,
+			       "Not supported");
+	return -1;
+}
+
+static struct mailbox_list_iterate_context *
+none_list_iter_init(struct mailbox_list *list,
+		    const char *const *patterns,
+		    enum mailbox_list_iter_flags flags)
+{
+	struct noop_list_iterate_context *ctx;
+	pool_t pool;
+
+	pool = pool_alloconly_create("mailbox list none iter", 1024);
+	ctx = p_new(pool, struct noop_list_iterate_context, 1);
+	ctx->ctx.pool = pool;
+	ctx->ctx.list = list;
+	ctx->ctx.flags = flags;
+	ctx->ctx.glob = imap_match_init_multiple(pool, patterns, TRUE,
+						 mail_namespace_get_sep(list->ns));
+	array_create(&ctx->ctx.module_contexts, pool, sizeof(void *), 5);
+	if ((list->ns->flags & NAMESPACE_FLAG_INBOX_USER) != 0 &&
+	    imap_match(ctx->ctx.glob, "INBOX") == IMAP_MATCH_YES) {
+		ctx->list_inbox = TRUE;
+		ctx->inbox_info.ns = list->ns;
+		ctx->inbox_info.vname = "INBOX";
+	}
+	return &ctx->ctx;
+}
+
+static int
+none_list_iter_deinit(struct mailbox_list_iterate_context *ctx)
+{
+	pool_unref(&ctx->pool);
+	return 0;
+}
+
+static const struct mailbox_info *
+none_list_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	struct noop_list_iterate_context *ctx =
+		(struct noop_list_iterate_context *)_ctx;
+
+	if (ctx->list_inbox) {
+		ctx->list_inbox = FALSE;
+		return &ctx->inbox_info;
+	}
+	return NULL;
+}
+
+static int
+none_list_get_mailbox_flags(struct mailbox_list *list ATTR_UNUSED,
+			    const char *dir ATTR_UNUSED,
+			    const char *fname ATTR_UNUSED,
+			    enum mailbox_list_file_type type ATTR_UNUSED,
+			    enum mailbox_info_flags *flags)
+{
+	*flags = MAILBOX_NONEXISTENT;
+	return 0;
+}
+
+struct mailbox_list none_mailbox_list = {
+	.name = MAILBOX_LIST_NAME_NONE,
+	.props = MAILBOX_LIST_PROP_NO_ROOT,
+	.mailbox_name_max_length = MAILBOX_LIST_NAME_MAX_LENGTH,
+
+	.v = {
+		.alloc = none_list_alloc,
+		.deinit = none_list_deinit,
+		.get_hierarchy_sep = none_list_get_hierarchy_sep,
+		.get_vname = mailbox_list_default_get_vname,
+		.get_storage_name = mailbox_list_default_get_storage_name,
+		.get_path = none_list_get_path,
+		.get_temp_prefix = none_list_get_temp_prefix,
+		.iter_init = none_list_iter_init,
+		.iter_next = none_list_iter_next,
+		.iter_deinit = none_list_iter_deinit,
+		.get_mailbox_flags = none_list_get_mailbox_flags,
+		.subscriptions_refresh = none_list_subscriptions_refresh,
+		.set_subscribed = none_list_set_subscribed,
+		.delete_mailbox = none_list_delete_mailbox,
+		.delete_dir = none_list_delete_dir,
+		.delete_symlink = none_list_delete_dir,
+		.rename_mailbox = none_list_rename_mailbox,
+	}
+};
diff --git a/src/lib-storage/list/mailbox-list-notify-tree.c b/src/lib-storage/list/mailbox-list-notify-tree.c
new file mode 100644
index 0000000..6152dbb
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-notify-tree.c
@@ -0,0 +1,131 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "mail-index.h"
+#include "mail-storage.h"
+#include "mailbox-list-private.h"
+#include "mailbox-list-index.h"
+#include "mailbox-list-notify-tree.h"
+
+struct mailbox_list_notify_tree {
+	struct mailbox_list *list;
+	struct mailbox_tree_context *mailboxes;
+
+	struct mail_index_view *view;
+	bool failed;
+};
+
+static void
+mailbox_list_notify_node_get_status(struct mailbox_list_notify_tree *tree,
+				    struct mailbox_notify_node *nnode)
+{
+	struct mailbox_status status;
+	const char *reason;
+	uint32_t seq;
+
+	if (!mail_index_lookup_seq(tree->view, nnode->index_uid, &seq))
+		return;
+
+	i_zero(&status);
+	(void)mailbox_list_index_status(tree->list, tree->view, seq,
+		STATUS_UIDVALIDITY | STATUS_UIDNEXT | STATUS_MESSAGES |
+		STATUS_UNSEEN | STATUS_HIGHESTMODSEQ, &status, nnode->guid,
+		NULL, &reason);
+	nnode->uidvalidity = status.uidvalidity;
+	nnode->uidnext = status.uidnext;
+	nnode->messages = status.messages;
+	nnode->unseen = status.unseen;
+	nnode->highest_modseq = status.highest_modseq;
+}
+
+static void
+mailbox_list_notify_node_build(struct mailbox_list_notify_tree *tree,
+			       struct mailbox_list_index_node *index_node,
+			       string_t *path)
+{
+	struct mailbox_node *node;
+	struct mailbox_notify_node *nnode;
+	size_t prefix_len;
+	bool created;
+
+	str_append(path, index_node->raw_name);
+
+	node = mailbox_tree_get(tree->mailboxes, str_c(path), &created);
+	nnode = (struct mailbox_notify_node *)node;
+	nnode->index_uid = index_node->uid;
+
+	if ((index_node->flags & MAILBOX_LIST_INDEX_FLAG_NONEXISTENT) != 0)
+		node->flags = MAILBOX_NONEXISTENT;
+	else if ((index_node->flags & MAILBOX_LIST_INDEX_FLAG_NOSELECT) != 0)
+		node->flags = MAILBOX_NOSELECT;
+	else {
+		node->flags = 0;
+		mailbox_list_notify_node_get_status(tree, nnode);
+	}
+	if ((index_node->flags & MAILBOX_LIST_INDEX_FLAG_NOINFERIORS) != 0)
+		node->flags |= MAILBOX_NOINFERIORS;
+
+	if (index_node->children != NULL) {
+		str_append_c(path, mailbox_list_get_hierarchy_sep(tree->list));
+		prefix_len = str_len(path);
+		index_node = index_node->children;
+		for (; index_node != NULL; index_node = index_node->next) {
+			str_truncate(path, prefix_len);
+			mailbox_list_notify_node_build(tree, index_node, path);
+		}
+	}
+}
+
+static void
+mailbox_list_notify_tree_build(struct mailbox_list_notify_tree *tree)
+{
+	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT_REQUIRE(tree->list);
+	struct mailbox_list_index_node *index_node;
+	string_t *path = t_str_new(128);
+
+	if (mailbox_list_index_refresh(tree->list) < 0)
+		tree->failed = TRUE;
+
+	tree->view = mail_index_view_open(ilist->index);
+	index_node = ilist->mailbox_tree;
+	for (; index_node != NULL; index_node = index_node->next) {
+		str_truncate(path, 0);
+		mailbox_list_notify_node_build(tree, index_node, path);
+	}
+	mail_index_view_close(&tree->view);
+}
+
+struct mailbox_list_notify_tree *
+mailbox_list_notify_tree_init(struct mailbox_list *list)
+{
+	struct mailbox_list_notify_tree *tree;
+
+	tree = i_new(struct mailbox_list_notify_tree, 1);
+	tree->list = list;
+	tree->mailboxes =
+		mailbox_tree_init_size(mailbox_list_get_hierarchy_sep(list),
+				       sizeof(struct mailbox_notify_node));
+	mailbox_list_notify_tree_build(tree);
+	return tree;
+}
+
+void mailbox_list_notify_tree_deinit(struct mailbox_list_notify_tree **_tree)
+{
+	struct mailbox_list_notify_tree *tree = *_tree;
+
+	*_tree = NULL;
+
+	mailbox_tree_deinit(&tree->mailboxes);
+	i_free(tree);
+}
+
+struct mailbox_notify_node *
+mailbox_list_notify_tree_lookup(struct mailbox_list_notify_tree *tree,
+				const char *storage_name)
+{
+	struct mailbox_node *node;
+
+	node = mailbox_tree_lookup(tree->mailboxes, storage_name);
+	return (struct mailbox_notify_node *)node;
+}
diff --git a/src/lib-storage/list/mailbox-list-notify-tree.h b/src/lib-storage/list/mailbox-list-notify-tree.h
new file mode 100644
index 0000000..3666ac8
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-notify-tree.h
@@ -0,0 +1,27 @@
+#ifndef MAILBOX_LIST_NOTIFY_TREE_H
+#define MAILBOX_LIST_NOTIFY_TREE_H
+
+#include "mailbox-tree.h"
+
+struct mailbox_notify_node {
+	struct mailbox_node node;
+
+	guid_128_t guid;
+	uint32_t index_uid;
+
+	uint32_t uidvalidity;
+	uint32_t uidnext;
+	uint32_t messages;
+	uint32_t unseen;
+	uint64_t highest_modseq;
+};
+
+struct mailbox_list_notify_tree *
+mailbox_list_notify_tree_init(struct mailbox_list *list);
+void mailbox_list_notify_tree_deinit(struct mailbox_list_notify_tree **tree);
+
+struct mailbox_notify_node *
+mailbox_list_notify_tree_lookup(struct mailbox_list_notify_tree *tree,
+				const char *storage_name);
+
+#endif
diff --git a/src/lib-storage/list/mailbox-list-subscriptions.c b/src/lib-storage/list/mailbox-list-subscriptions.c
new file mode 100644
index 0000000..2e27c96
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-subscriptions.c
@@ -0,0 +1,318 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "array.h"
+#include "unichar.h"
+#include "imap-match.h"
+#include "subscription-file.h"
+#include "mailbox-tree.h"
+#include "mailbox-list-private.h"
+#include "mailbox-list-subscriptions.h"
+
+#include <sys/stat.h>
+
+struct subscriptions_mailbox_list_iterate_context {
+	struct mailbox_list_iterate_context ctx;
+	struct mailbox_tree_context *tree;
+	struct mailbox_tree_iterate_context *iter;
+	struct mailbox_info info;
+};
+
+static int
+mailbox_list_subscription_fill_one(struct mailbox_list *list,
+				   struct mailbox_list *src_list,
+				   const char *name)
+{
+	struct mail_namespace *ns, *default_ns = list->ns;
+	struct mail_namespace *namespaces = default_ns->user->namespaces;
+	struct mailbox_node *node;
+	const char *vname, *ns_name, *error;
+	size_t len;
+	bool created;
+
+	/* default_ns is whatever namespace we're currently listing.
+	   if we have e.g. prefix="" and prefix=pub/ namespaces with
+	   pub/ namespace having subscriptions=no, we want to:
+
+	   1) when listing "" namespace we want to skip over any names
+	   that begin with pub/. */
+	if (src_list->ns->prefix_len == 0)
+		ns_name = name;
+	else {
+		/* we could have two-level namespace: ns/ns2/ */
+		ns_name = t_strconcat(src_list->ns->prefix, name, NULL);
+	}
+	ns = mail_namespace_find_unsubscribable(namespaces, ns_name);
+	if (ns != NULL && ns != default_ns) {
+		if (ns->prefix_len > 0)
+			return 0;
+		/* prefix="" namespace=no : catching this is basically the
+		   same as not finding any namespace. */
+		ns = NULL;
+	}
+
+	/* 2) when listing pub/ namespace, skip over entries that don't
+	   begin with pub/. */
+	if (ns == NULL &&
+	    (default_ns->flags & NAMESPACE_FLAG_SUBSCRIPTIONS) == 0)
+		return 0;
+
+	/* When listing shared namespace's subscriptions, we need to
+	   autocreate all the visible child namespaces. their subscriptions
+	   are listed later. */
+	if (ns != NULL && mail_namespace_is_shared_user_root(ns)) {
+		/* we'll need to get the namespace autocreated.
+		   one easy way is to just ask to join a reference and
+		   pattern */
+		(void)mailbox_list_join_refpattern(ns->list, ns_name, "");
+	}
+
+	/* When listing pub/ namespace, skip over the namespace
+	   prefix in the name. the rest of the name is storage_name. */
+	if (ns == NULL)
+		ns = default_ns;
+	else if (strncmp(ns_name, ns->prefix, ns->prefix_len) == 0) {
+		ns_name += ns->prefix_len;
+		name = ns_name;
+	} else {
+		/* "pub" entry - this shouldn't be possible normally, because
+		   it should be saved as "pub/", but handle it anyway */
+		i_assert(strncmp(ns_name, ns->prefix, ns->prefix_len-1) == 0 &&
+			 ns_name[ns->prefix_len-1] == '\0');
+		name = "";
+		/* ns_name = ""; */
+	}
+
+	len = strlen(name);
+	if (len > 0 && name[len-1] == mail_namespace_get_sep(ns)) {
+		/* entry ends with hierarchy separator, remove it.
+		   this exists mainly for backwards compatibility with old
+		   Dovecot versions and non-Dovecot software that added them */
+		name = t_strndup(name, len-1);
+	}
+
+	if (!mailbox_list_is_valid_name(list, name, &error)) {
+		/* we'll only get into trouble if we show this */
+		return -1;
+	} else {
+		vname = mailbox_list_get_vname(list, name);
+		if (!uni_utf8_str_is_valid(vname))
+			return -1;
+		node = mailbox_tree_get(list->subscriptions, vname, &created);
+		node->flags = MAILBOX_SUBSCRIBED;
+	}
+	return 0;
+}
+
+int mailbox_list_subscriptions_refresh(struct mailbox_list *src_list,
+				       struct mailbox_list *dest_list)
+{
+	struct subsfile_list_context *subsfile_ctx;
+	struct stat st;
+	enum mailbox_list_path_type type;
+	const char *path, *name;
+	char sep;
+	int ret;
+
+	/* src_list is subscriptions=yes, dest_list is subscriptions=no
+	   (or the same as src_list) */
+	i_assert((src_list->ns->flags & NAMESPACE_FLAG_SUBSCRIPTIONS) != 0);
+
+	if (dest_list->subscriptions == NULL) {
+		sep = mail_namespace_get_sep(src_list->ns);
+		dest_list->subscriptions = mailbox_tree_init(sep);
+	}
+
+	type = src_list->set.control_dir != NULL ?
+		MAILBOX_LIST_PATH_TYPE_CONTROL : MAILBOX_LIST_PATH_TYPE_DIR;
+	if (!mailbox_list_get_root_path(src_list, type, &path) ||
+	    src_list->set.subscription_fname == NULL) {
+		/* no subscriptions (e.g. pop3c) */
+		return 0;
+	}
+	path = t_strconcat(path, "/", src_list->set.subscription_fname, NULL);
+	if (stat(path, &st) < 0) {
+		if (errno == ENOENT) {
+			/* no subscriptions */
+			mailbox_tree_clear(dest_list->subscriptions);
+			dest_list->subscriptions_mtime = 0;
+			return 0;
+		}
+		mailbox_list_set_critical(dest_list, "stat(%s) failed: %m",
+					  path);
+		return -1;
+	}
+	if (st.st_mtime == dest_list->subscriptions_mtime &&
+	    st.st_mtime < dest_list->subscriptions_read_time-1) {
+		/* we're up to date */
+		return 0;
+	}
+
+	mailbox_tree_clear(dest_list->subscriptions);
+	dest_list->subscriptions_read_time = ioloop_time;
+
+	subsfile_ctx = subsfile_list_init(dest_list, path);
+	if (subsfile_list_fstat(subsfile_ctx, &st) == 0)
+		dest_list->subscriptions_mtime = st.st_mtime;
+	while ((name = subsfile_list_next(subsfile_ctx)) != NULL) T_BEGIN {
+		T_BEGIN {
+			ret = mailbox_list_subscription_fill_one(dest_list,
+								 src_list, name);
+		} T_END;
+		if (ret < 0) {
+			e_warning(dest_list->ns->user->event,
+				  "Subscriptions file %s: "
+				  "Removing invalid entry: %s",
+				  path, name);
+			(void)subsfile_set_subscribed(src_list, path,
+				mailbox_list_get_temp_prefix(src_list),
+				name, FALSE);
+
+		}
+	} T_END;
+
+	if (subsfile_list_deinit(&subsfile_ctx) < 0) {
+		dest_list->subscriptions_mtime = (time_t)-1;
+		return -1;
+	}
+	return 0;
+}
+
+void mailbox_list_set_subscription_flags(struct mailbox_list *list,
+					 const char *vname,
+					 enum mailbox_info_flags *flags)
+{
+	struct mailbox_node *node;
+
+	*flags &= ENUM_NEGATE(MAILBOX_SUBSCRIBED | MAILBOX_CHILD_SUBSCRIBED);
+
+	node = mailbox_tree_lookup(list->subscriptions, vname);
+	if (node != NULL) {
+		*flags |= node->flags & MAILBOX_SUBSCRIBED;
+
+		/* the only reason why node might have a child is if one of
+		   them is subscribed */
+		if (node->children != NULL)
+			*flags |= MAILBOX_CHILD_SUBSCRIBED;
+	}
+}
+
+void mailbox_list_subscriptions_fill(struct mailbox_list_iterate_context *ctx,
+				     struct mailbox_tree_context *tree,
+				     bool default_nonexistent)
+{
+	struct mailbox_list_iter_update_context update_ctx;
+	struct mailbox_tree_iterate_context *iter;
+	const char *name;
+
+	i_zero(&update_ctx);
+	update_ctx.iter_ctx = ctx;
+	update_ctx.tree_ctx = tree;
+	update_ctx.glob = ctx->glob;
+	update_ctx.leaf_flags = MAILBOX_SUBSCRIBED;
+	if (default_nonexistent)
+		update_ctx.leaf_flags |= MAILBOX_NONEXISTENT;
+	update_ctx.parent_flags = MAILBOX_CHILD_SUBSCRIBED;
+	update_ctx.match_parents =
+		(ctx->flags & MAILBOX_LIST_ITER_SELECT_RECURSIVEMATCH) != 0;
+
+	iter = mailbox_tree_iterate_init(ctx->list->subscriptions, NULL,
+					 MAILBOX_SUBSCRIBED);
+	while (mailbox_tree_iterate_next(iter, &name) != NULL)
+		mailbox_list_iter_update(&update_ctx, name);
+	mailbox_tree_iterate_deinit(&iter);
+}
+
+struct mailbox_list_iterate_context *
+mailbox_list_subscriptions_iter_init(struct mailbox_list *list,
+				     const char *const *patterns,
+				     enum mailbox_list_iter_flags flags)
+{
+	struct subscriptions_mailbox_list_iterate_context *ctx;
+	pool_t pool;
+	char sep = mail_namespace_get_sep(list->ns);
+
+	pool = pool_alloconly_create("mailbox list subscriptions iter", 1024);
+	ctx = p_new(pool, struct subscriptions_mailbox_list_iterate_context, 1);
+	ctx->ctx.pool = pool;
+	ctx->ctx.list = list;
+	ctx->ctx.flags = flags;
+	ctx->ctx.glob = imap_match_init_multiple(pool, patterns, TRUE, sep);
+	array_create(&ctx->ctx.module_contexts, pool, sizeof(void *), 5);
+
+	ctx->tree = mailbox_tree_init(sep);
+	mailbox_list_subscriptions_fill(&ctx->ctx, ctx->tree, FALSE);
+
+	ctx->info.ns = list->ns;
+	/* the tree usually has only those entries we want to iterate through,
+	   but there are also non-matching root entries (e.g. "LSUB foo/%" will
+	   include the "foo"), which we'll drop with MAILBOX_MATCHED. */
+	ctx->iter = mailbox_tree_iterate_init(ctx->tree, NULL, MAILBOX_MATCHED);
+	return &ctx->ctx;
+}
+
+const struct mailbox_info *
+mailbox_list_subscriptions_iter_next(struct mailbox_list_iterate_context *_ctx)
+{
+	struct subscriptions_mailbox_list_iterate_context *ctx =
+		(struct subscriptions_mailbox_list_iterate_context *)_ctx;
+	struct mailbox_list *list = _ctx->list;
+	struct mailbox_node *node;
+	enum mailbox_info_flags subs_flags;
+	const char *vname, *storage_name, *error;
+	int ret;
+
+	node = mailbox_tree_iterate_next(ctx->iter, &vname);
+	if (node == NULL)
+		return mailbox_list_iter_default_next(_ctx);
+
+	ctx->info.vname = vname;
+	subs_flags = node->flags & (MAILBOX_SUBSCRIBED |
+				    MAILBOX_CHILD_SUBSCRIBED);
+
+	if ((_ctx->flags & MAILBOX_LIST_ITER_RETURN_NO_FLAGS) != 0 &&
+	    (_ctx->flags & MAILBOX_LIST_ITER_RETURN_CHILDREN) == 0) {
+		/* don't care about flags, just return it */
+		ctx->info.flags = subs_flags;
+		return &ctx->info;
+	}
+
+	storage_name = mailbox_list_get_storage_name(list, vname);
+	if (!mailbox_list_is_valid_name(list, storage_name, &error)) {
+		/* broken entry in subscriptions file */
+		ctx->info.flags = MAILBOX_NONEXISTENT;
+	} else if (mailbox_list_mailbox(list, storage_name,
+					&ctx->info.flags) < 0) {
+		ctx->info.flags = 0;
+		_ctx->failed = TRUE;
+	} else if ((_ctx->flags & MAILBOX_LIST_ITER_RETURN_CHILDREN) != 0 &&
+		   (ctx->info.flags & (MAILBOX_CHILDREN |
+				       MAILBOX_NOCHILDREN)) == 0) {
+		ret = mailbox_has_children(list, storage_name);
+		if (ret < 0)
+			_ctx->failed = TRUE;
+		else if (ret == 0)
+			ctx->info.flags |= MAILBOX_NOCHILDREN;
+		else
+			ctx->info.flags |= MAILBOX_CHILDREN;
+
+	}
+
+	ctx->info.flags &= ENUM_NEGATE(MAILBOX_SUBSCRIBED | MAILBOX_CHILD_SUBSCRIBED);
+	ctx->info.flags |=
+		node->flags & (MAILBOX_SUBSCRIBED | MAILBOX_CHILD_SUBSCRIBED);
+	return &ctx->info;
+}
+
+int mailbox_list_subscriptions_iter_deinit(struct mailbox_list_iterate_context *_ctx)
+{
+	struct subscriptions_mailbox_list_iterate_context *ctx =
+		(struct subscriptions_mailbox_list_iterate_context *)_ctx;
+	int ret = _ctx->failed ? -1 : 0;
+
+	mailbox_tree_iterate_deinit(&ctx->iter);
+	mailbox_tree_deinit(&ctx->tree);
+	pool_unref(&_ctx->pool);
+	return ret;
+}
diff --git a/src/lib-storage/list/mailbox-list-subscriptions.h b/src/lib-storage/list/mailbox-list-subscriptions.h
new file mode 100644
index 0000000..283012d
--- /dev/null
+++ b/src/lib-storage/list/mailbox-list-subscriptions.h
@@ -0,0 +1,33 @@
+#ifndef MAILBOX_LIST_SUBSCRIPTIONS_H
+#define MAILBOX_LIST_SUBSCRIPTIONS_H
+
+#include "mailbox-list-iter.h"
+
+struct mailbox_tree_context;
+struct mailbox_list_iterate_context;
+
+int mailbox_list_subscriptions_refresh(struct mailbox_list *src_list,
+				       struct mailbox_list *dest_list);
+
+/* Set MAILBOX_SUBSCRIBED and MAILBOX_CHILD_SUBSCRIBED flags,
+   clearing them if they already are there when they shouldn't. */
+void mailbox_list_set_subscription_flags(struct mailbox_list *list,
+					 const char *vname,
+					 enum mailbox_info_flags *flags);
+
+/* Add subscriptions matching the iteration to the given tree */
+void mailbox_list_subscriptions_fill(struct mailbox_list_iterate_context *ctx,
+				     struct mailbox_tree_context *tree,
+				     bool default_nonexistent);
+
+/* Iterate through subscriptions, call mailbox_list.get_mailbox_flags()
+   if necessary for mailboxes to get their flags. */
+struct mailbox_list_iterate_context *
+mailbox_list_subscriptions_iter_init(struct mailbox_list *list,
+				     const char *const *patterns,
+				     enum mailbox_list_iter_flags flags);
+const struct mailbox_info *
+mailbox_list_subscriptions_iter_next(struct mailbox_list_iterate_context *ctx);
+int mailbox_list_subscriptions_iter_deinit(struct mailbox_list_iterate_context *ctx);
+
+#endif
diff --git a/src/lib-storage/list/subscription-file.c b/src/lib-storage/list/subscription-file.c
new file mode 100644
index 0000000..4c5094a
--- /dev/null
+++ b/src/lib-storage/list/subscription-file.c
@@ -0,0 +1,380 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "strescape.h"
+#include "istream.h"
+#include "ostream.h"
+#include "nfs-workarounds.h"
+#include "mkdir-parents.h"
+#include "file-dotlock.h"
+#include "mailbox-list-private.h"
+#include "subscription-file.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+
+#define SUBSCRIPTION_FILE_ESTALE_RETRY_COUNT NFS_ESTALE_RETRY_COUNT
+#define SUBSCRIPTION_FILE_LOCK_TIMEOUT 120
+#define SUBSCRIPTION_FILE_CHANGE_TIMEOUT 30
+
+struct subsfile_list_context {
+	struct mailbox_list *list;
+	struct istream *input;
+	char *path;
+	string_t *name;
+
+	unsigned int version;
+	bool failed;
+};
+
+static const char version2_header[] = "V\t2\n\n";
+
+static void subsread_set_syscall_error(struct mailbox_list *list,
+				       const char *function, const char *path)
+{
+	if (errno == EACCES && !event_want_debug_log(list->ns->user->event)) {
+		mailbox_list_set_error(list, MAIL_ERROR_PERM,
+				       "No permission to read subscriptions");
+	} else {
+		mailbox_list_set_critical(list,
+			"%s failed with subscription file %s: %m",
+			function, path);
+	}
+}
+
+static void subswrite_set_syscall_error(struct mailbox_list *list,
+					const char *function, const char *path)
+{
+	if (errno == EACCES && !event_want_debug_log(list->ns->user->event)) {
+		mailbox_list_set_error(list, MAIL_ERROR_PERM,
+				       "No permission to modify subscriptions");
+	} else {
+		mailbox_list_set_critical(list,
+			"%s failed with subscription file %s: %m",
+			function, path);
+	}
+}
+
+static void
+subsfile_list_read_header(struct mailbox_list *list, struct istream *input,
+			  unsigned int *version_r)
+{
+	const unsigned char version2_header_len = strlen(version2_header);
+	const unsigned char *data;
+	size_t size;
+	int ret;
+
+	*version_r = 0;
+
+	ret = i_stream_read_bytes(input, &data, &size, version2_header_len);
+	if (ret < 0) {
+		i_assert(ret == -1);
+		if (input->stream_errno != 0)
+			subswrite_set_syscall_error(list, "read()", i_stream_get_name(input));
+		return;
+	}
+	if (ret > 0 &&
+	    memcmp(data, version2_header, version2_header_len) == 0) {
+		*version_r = 2;
+		i_stream_skip(input, version2_header_len);
+	}
+}
+
+static const char *next_line(struct mailbox_list *list, const char *path,
+			     struct istream *input, bool *failed_r,
+			     bool ignore_estale)
+{
+	const char *line;
+
+	*failed_r = FALSE;
+
+	while ((line = i_stream_next_line(input)) == NULL) {
+                switch (i_stream_read(input)) {
+		case -1:
+                        if (input->stream_errno != 0 &&
+                            (input->stream_errno != ESTALE || !ignore_estale)) {
+                                subswrite_set_syscall_error(list,
+							    "read()", path);
+                                *failed_r = TRUE;
+                        }
+			return NULL;
+		case -2:
+			/* mailbox name too large */
+			mailbox_list_set_critical(list,
+				"Subscription file %s contains lines longer "
+				"than %u characters", path,
+				(unsigned int)list->mailbox_name_max_length);
+			*failed_r = TRUE;
+			return NULL;
+		}
+	}
+
+	return line;
+}
+
+int subsfile_set_subscribed(struct mailbox_list *list, const char *path,
+			    const char *temp_prefix, const char *name,
+			    bool set)
+{
+	const struct mail_storage_settings *mail_set = list->mail_set;
+	struct dotlock_settings dotlock_set;
+	struct dotlock *dotlock;
+	struct mailbox_permissions perm;
+	const char *line, *dir, *fname, *escaped_name;
+	struct istream *input = NULL;
+	struct ostream *output;
+	int fd_in, fd_out;
+	enum mailbox_list_path_type type;
+	bool found, changed = FALSE, failed = FALSE;
+	unsigned int version = 2;
+
+	if (strcasecmp(name, "INBOX") == 0)
+		name = "INBOX";
+
+	i_zero(&dotlock_set);
+	dotlock_set.use_excl_lock = mail_set->dotlock_use_excl;
+	dotlock_set.nfs_flush = mail_set->mail_nfs_storage;
+	dotlock_set.temp_prefix = temp_prefix;
+	dotlock_set.timeout = SUBSCRIPTION_FILE_LOCK_TIMEOUT;
+	dotlock_set.stale_timeout = SUBSCRIPTION_FILE_CHANGE_TIMEOUT;
+
+	mailbox_list_get_root_permissions(list, &perm);
+	fd_out = file_dotlock_open_group(&dotlock_set, path, 0,
+					 perm.file_create_mode,
+					 perm.file_create_gid,
+					 perm.file_create_gid_origin, &dotlock);
+	if (fd_out == -1 && errno == ENOENT) {
+		/* directory hasn't been created yet. */
+		type = list->set.control_dir != NULL ?
+			MAILBOX_LIST_PATH_TYPE_CONTROL :
+			MAILBOX_LIST_PATH_TYPE_DIR;
+		fname = strrchr(path, '/');
+		if (fname != NULL) {
+			dir = t_strdup_until(path, fname);
+			if (mailbox_list_mkdir_root(list, dir, type) < 0)
+				return -1;
+		}
+		fd_out = file_dotlock_open_group(&dotlock_set, path, 0,
+						 perm.file_create_mode,
+						 perm.file_create_gid,
+						 perm.file_create_gid_origin,
+						 &dotlock);
+	}
+	if (fd_out == -1) {
+		if (errno == EAGAIN) {
+			mailbox_list_set_error(list, MAIL_ERROR_TEMP,
+				"Timeout waiting for subscription file lock");
+		} else {
+			subswrite_set_syscall_error(list, "file_dotlock_open()",
+						    path);
+		}
+		return -1;
+	}
+
+	fd_in = nfs_safe_open(path, O_RDONLY);
+	if (fd_in == -1 && errno != ENOENT) {
+		subswrite_set_syscall_error(list, "open()", path);
+		file_dotlock_delete(&dotlock);
+		return -1;
+	}
+	if (fd_in != -1) {
+		input = i_stream_create_fd_autoclose(&fd_in, list->mailbox_name_max_length+1);
+		i_stream_set_return_partial_line(input, TRUE);
+		subsfile_list_read_header(list, input, &version);
+	}
+
+	found = FALSE;
+	output = o_stream_create_fd_file(fd_out, 0, FALSE);
+	o_stream_cork(output);
+	if (version >= 2)
+		o_stream_nsend_str(output, version2_header);
+	if (version < 2 || name[0] == '\0')
+		escaped_name = name;
+	else {
+		const char *const *tmp;
+		char separators[2];
+		string_t *str = t_str_new(64);
+
+		separators[0] = mailbox_list_get_hierarchy_sep(list);
+		separators[1] = '\0';
+		tmp = t_strsplit(name, separators);
+		str_append_tabescaped(str, *tmp);
+		for (tmp++; *tmp != NULL; tmp++) {
+			str_append_c(str, '\t');
+			str_append_tabescaped(str, *tmp);
+		}
+		escaped_name = str_c(str);
+	}
+	if (input != NULL) {
+		while ((line = next_line(list, path, input,
+					 &failed, FALSE)) != NULL) {
+			if (strcmp(line, escaped_name) == 0) {
+				found = TRUE;
+				if (!set) {
+					changed = TRUE;
+					continue;
+				}
+			}
+
+			o_stream_nsend_str(output, line);
+			o_stream_nsend(output, "\n", 1);
+		}
+		i_stream_destroy(&input);
+	}
+
+	if (!failed && set && !found) {
+		/* append subscription */
+		line = t_strconcat(escaped_name, "\n", NULL);
+		o_stream_nsend_str(output, line);
+		changed = TRUE;
+	}
+
+	if (changed && !failed) {
+		if (o_stream_finish(output) < 0) {
+			subswrite_set_syscall_error(list, "write()", path);
+			failed = TRUE;
+		} else if (mail_set->parsed_fsync_mode != FSYNC_MODE_NEVER) {
+			if (fsync(fd_out) < 0) {
+				subswrite_set_syscall_error(list, "fsync()",
+							    path);
+				failed = TRUE;
+			}
+		}
+	} else {
+		o_stream_abort(output);
+	}
+	o_stream_destroy(&output);
+
+	if (failed || !changed) {
+		if (file_dotlock_delete(&dotlock) < 0) {
+			subswrite_set_syscall_error(list,
+				"file_dotlock_delete()", path);
+			failed = TRUE;
+		}
+	} else {
+		enum dotlock_replace_flags flags =
+			DOTLOCK_REPLACE_FLAG_VERIFY_OWNER;
+		if (file_dotlock_replace(&dotlock, flags) < 0) {
+			subswrite_set_syscall_error(list,
+				"file_dotlock_replace()", path);
+			failed = TRUE;
+		}
+	}
+	return failed ? -1 : (changed ? 1 : 0);
+}
+
+struct subsfile_list_context *
+subsfile_list_init(struct mailbox_list *list, const char *path)
+{
+	struct subsfile_list_context *ctx;
+	int fd;
+
+	ctx = i_new(struct subsfile_list_context, 1);
+	ctx->list = list;
+
+	fd = nfs_safe_open(path, O_RDONLY);
+	if (fd == -1) {
+		if (errno != ENOENT) {
+			subsread_set_syscall_error(list, "open()", path);
+			ctx->failed = TRUE;
+		}
+	} else {
+		ctx->input = i_stream_create_fd_autoclose(&fd,
+					list->mailbox_name_max_length+1);
+		i_stream_set_return_partial_line(ctx->input, TRUE);
+		subsfile_list_read_header(ctx->list, ctx->input, &ctx->version);
+	}
+	ctx->path = i_strdup(path);
+	ctx->name = str_new(default_pool, 128);
+	return ctx;
+}
+
+int subsfile_list_deinit(struct subsfile_list_context **_ctx)
+{
+	struct subsfile_list_context *ctx = *_ctx;
+	int ret = ctx->failed ? -1 : 0;
+
+	*_ctx = NULL;
+
+	i_stream_destroy(&ctx->input);
+	str_free(&ctx->name);
+	i_free(ctx->path);
+	i_free(ctx);
+	return ret;
+}
+
+int subsfile_list_fstat(struct subsfile_list_context *ctx, struct stat *st_r)
+{
+	const struct stat *st;
+
+	if (ctx->failed)
+		return -1;
+
+	if (i_stream_stat(ctx->input, FALSE, &st) < 0) {
+		ctx->failed = TRUE;
+		return -1;
+	}
+	*st_r = *st;
+	return 0;
+}
+
+static const char *
+subsfile_list_unescaped(struct subsfile_list_context *ctx, const char *line)
+{
+	const char *p;
+
+	str_truncate(ctx->name, 0);
+	while ((p = strchr(line, '\t')) != NULL) {
+		str_append_tabunescaped(ctx->name, line, p-line);
+		str_append_c(ctx->name, mailbox_list_get_hierarchy_sep(ctx->list));
+		line = p+1;
+	}
+	str_append_tabunescaped(ctx->name, line, strlen(line));
+	return str_c(ctx->name);
+}
+
+const char *subsfile_list_next(struct subsfile_list_context *ctx)
+{
+        const char *line;
+        unsigned int i;
+        int fd;
+
+        if (ctx->failed || ctx->input == NULL)
+		return NULL;
+
+        for (i = 0;; i++) {
+                line = next_line(ctx->list, ctx->path, ctx->input, &ctx->failed,
+				 i < SUBSCRIPTION_FILE_ESTALE_RETRY_COUNT);
+		if (ctx->input->stream_errno != ESTALE ||
+                    i == SUBSCRIPTION_FILE_ESTALE_RETRY_COUNT)
+                        break;
+
+                /* Reopen the subscription file and re-send everything.
+                   this isn't the optimal behavior, but it's allowed by
+                   IMAP and this way we don't have to read everything into
+                   memory or try to play any guessing games. */
+                i_stream_destroy(&ctx->input);
+
+                fd = nfs_safe_open(ctx->path, O_RDONLY);
+                if (fd == -1) {
+                        /* In case of ENOENT all the subscriptions got lost.
+                           Just return end of subscriptions list in that
+                           case. */
+                        if (errno != ENOENT) {
+                                subsread_set_syscall_error(ctx->list, "open()",
+							   ctx->path);
+                                ctx->failed = TRUE;
+                        }
+                        return NULL;
+                }
+
+		ctx->input = i_stream_create_fd_autoclose(&fd,
+					ctx->list->mailbox_name_max_length+1);
+		i_stream_set_return_partial_line(ctx->input, TRUE);
+	}
+
+	if (ctx->version > 1 && line != NULL)
+		line = subsfile_list_unescaped(ctx, line);
+        return line;
+}
diff --git a/src/lib-storage/list/subscription-file.h b/src/lib-storage/list/subscription-file.h
new file mode 100644
index 0000000..fbaa0a3
--- /dev/null
+++ b/src/lib-storage/list/subscription-file.h
@@ -0,0 +1,25 @@
+#ifndef SUBSCRIPTION_FILE_H
+#define SUBSCRIPTION_FILE_H
+
+struct stat;
+struct mailbox_list;
+
+/* Initialize new subscription file listing. */
+struct subsfile_list_context *
+subsfile_list_init(struct mailbox_list *list, const char *path);
+/* Deinitialize subscription file listing. Returns 0 if ok, or -1 if some
+   error occurred while listing. */
+int subsfile_list_deinit(struct subsfile_list_context **ctx);
+
+/* Call fstat() for subscription file */
+int subsfile_list_fstat(struct subsfile_list_context *ctx, struct stat *st_r);
+
+/* Returns the next subscribed mailbox, or NULL. */
+const char *subsfile_list_next(struct subsfile_list_context *ctx);
+
+/* Returns 1 if subscribed, 0 if no changes done, -1 if error. */
+int subsfile_set_subscribed(struct mailbox_list *list, const char *path,
+			    const char *temp_prefix, const char *name,
+			    bool set);
+
+#endif