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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 19:59:03 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 19:59:03 +0000
commita848231ae0f346dc7cc000973fbeb65b0894ee92 (patch)
tree44b60b367c86723cc78383ef247885d72b388afe /src/global/smtputf8.h
parentInitial commit. (diff)
downloadpostfix-a848231ae0f346dc7cc000973fbeb65b0894ee92.tar.xz
postfix-a848231ae0f346dc7cc000973fbeb65b0894ee92.zip
Adding upstream version 3.8.5.upstream/3.8.5
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+#ifndef _SMTPUTF8_H_INCLUDED_
+#define _SMTPUTF8_H_INCLUDED_
+
+/*++
+/* NAME
+/* smtputf8 3h
+/* SUMMARY
+/* SMTPUTF8 support
+/* SYNOPSIS
+/* #include <smtputf8.h>
+/* DESCRIPTION
+/* .nf
+
+ /*
+ * Avoiding chicken-and-egg problems during the initial SMTPUTF8 roll-out in
+ * environments with pre-existing mail flows that contain UTF8.
+ *
+ * Prior to SMTPUTF8, mail flows that contain UTF8 worked because the vast
+ * majority of MTAs is perfectly capable of handling UTF8 in address
+ * localparts (and in headers), even if pre-SMTPUTF8 standards do not
+ * support this practice.
+ *
+ * When turning on Postfix SMTPUTF8 support for the first time, we don't want
+ * to suddenly break pre-existing mail flows that contain UTF8 because 1) a
+ * client does not request SMTPUTF8 support, and because 2) a down-stream
+ * MTA does not announce SMTPUTF8 support.
+ *
+ * While 1) is easy enough to avoid (keep accepting UTF8 in address localparts
+ * just like Postfix has always done), 2) presents a thornier problem. The
+ * root cause of that problem is the need for SMTPUTF8 autodetection.
+ *
+ * What is SMTPUTF8 autodetection? Postfix cannot rely solely on the sender's
+ * declaration that a message requires SMTPUTF8 support, because UTF8 may be
+ * introduced during local processing (for example, the client hostname in
+ * Postfix's Received: header, adding @$myorigin or .$mydomain to an
+ * incomplete address, address rewriting, alias expansion, automatic BCC
+ * recipients, local forwarding, and changes made by header checks or Milter
+ * applications).
+ *
+ * In summary, after local processing has happened, Postfix may decide that a
+ * message requires SMTPUTF8 support, even when that message initially did
+ * not require SMTPUTF8 support. This could make the message undeliverable
+ * to destinations that do not support SMTPUTF8. In an environment with
+ * pre-existing mail flows that contain UTF8, we want to avoid disrupting
+ * those mail flows when rolling out SMTPUTF8 support.
+ *
+ * For the vast majority of sites, the simplest solution is to autodetect
+ * SMTPUTF8 support only for Postfix sendmail command-line submissions, at
+ * least as long as SMTPUTF8 support has not yet achieved wold domination.
+ *
+ * However, sites that add UTF8 content via local processing (see above) should
+ * autodetect SMTPUTF8 support for all email.
+ *
+ * smtputf8_autodetect() uses the setting of the smtputf8_autodetect_classes
+ * parameter, and the mail source classes defined in mail_params.h.
+ */
+extern int smtputf8_autodetect(int);
+
+ /*
+ * The flag SMTPUTF8_FLAG_REQUESTED is raised on request by the sender, or
+ * when a queue file contains at least one UTF8 envelope recipient. One this
+ * flag is raised it is preserved when mail is forwarded or bounced.
+ *
+ * The flag SMTPUTF8_FLAG_HEADER is raised when a queue file contains at least
+ * one UTF8 message header.
+ *
+ * The flag SMTPUTF8_FLAG_SENDER is raised when a queue file contains an UTF8
+ * envelope sender.
+ *
+ * The three flags SMTPUTF8_FLAG_REQUESTED/HEADER/SENDER are stored in the
+ * queue file, are sent with delivery requests to Postfix delivery agents,
+ * and are sent with "flush" requests to the bounce daemon to ensure that
+ * the resulting notification message will have a content-transfer-encoding
+ * of 8bit.
+ *
+ * In the future, mailing lists will have a mix of UTF8 and non-UTF8
+ * subscribers. With the following flag, Postfix can avoid requiring
+ * SMTPUTF8 delivery when it isn't really needed.
+ *
+ * The flag SMTPUTF8_FLAG_RECIPIENT is raised when a delivery request (NOT:
+ * message) contains at least one UTF8 envelope recipient. The flag is NOT
+ * stored in the queue file. The flag sent in requests to the bounce daemon
+ * ONLY when bouncing a single recipient. The flag is used ONLY in requests
+ * to Postfix delivery agents, to give Postfix flexibility when delivering
+ * messages to non-SMTPUTF8 servers.
+ *
+ * If a delivery request has none of the flags SMTPUTF8_FLAG_RECIPIENT,
+ * SMTPUTF8_FLAG_SENDER, or SMTPUTF8_FLAG_HEADER, then the message can
+ * safely be delivered to a non-SMTPUTF8 server (DSN original recipients
+ * will be encoded appropriately per RFC 6533).
+ *
+ * To allow even more SMTPUTF8 mail to be sent to non-SMTPUTF8 servers,
+ * implement RFC 2047 header encoding in the Postfix SMTP client, and update
+ * the SMTP client protocol engine.
+ */
+#define SMTPUTF8_FLAG_NONE (0)
+#define SMTPUTF8_FLAG_REQUESTED (1<<0) /* queue file/delivery/bounce request */
+#define SMTPUTF8_FLAG_HEADER (1<<1) /* queue file/delivery/bounce request */
+#define SMTPUTF8_FLAG_SENDER (1<<2) /* queue file/delivery/bounce request */
+#define SMTPUTF8_FLAG_RECIPIENT (1<<3) /* delivery request only */
+
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+#endif