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+Wish list:
+
+ Things to do before the stable release:
+
+ make pre-release-check, HTML validator check.
+
+ Disable -DSNAPSHOT and -DNONPROD in makedefs.
+
+ Alias htable(3) calls to equivalent binhash(3) calls,
+ and obsolete the htable(3) module.
+
+ FILTER_README needs some text on multi-instance implementations,
+ and existing multi-instance references need to be updated.
+
+ Fix code that still uses "long" for data_size and data_offset,
+ and that uses "%ld" in sscanf().
+
+ A smart query service for live Postfix tables that outputs JSON?
+
+ Add a pointer to
+ http://mmogilvi.users.sourceforge.net/software/oauthbearer.html
+ in documentation or on-line howtos.
+
+ Read http://mmogilvi.users.sourceforge.net/software/oauthbearer.html
+ and see how we can improve on the Postfix side.
+
+ Add verp=+= to the qmgr "from=" logging. This is already
+ implemented but not yet integrated.
+
+ Need canonical Dovecot example that has virtual_mailbox_domains,
+ (virtual_mailbox_maps or reject unverified_recipient), and
+ virtual_transport.
+
+ Make smtpd_relay_before_recipient_restrictions settable
+ in smtpd_checks tests.
+
+ Make the DNS resolver library pluggable, so that we can a)
+ plug in a fake resolver library for DNS-related regression
+ tests and make DNS tests hermetic (no external dependency;
+ b) add support for non-libbind resolvers. Gracefully handle
+ requests for unsupported functionality; return an error status,
+ instead of terminating.
+
+ Add a robust dnssec_probe regression test (success and fail)
+ that does not break existing regression tests.
+
+ smtp_sasl_tls_security_options = noanonymous, and make
+ smtp_sasl_security_options the default dependent on the
+ smtp_sasl_tls_security_options default (i.e. reverse the
+ dependency). Or make them independent.
+
+ Try to make the master throttle more distrusting. Currently,
+ the master throttles a service after a child process cannot be
+ created (fork() fails), or if a child process fails upon its
+ first use. The master always unthrottles the service if a process
+ handles a client successfully. This is sufficient to mitigate
+ local errors that break all attempts to use a service. It also
+ slows down stupid remote attacks as long as malicious traffic
+ dominates benign traffic. Perhaps monitor a crashing percentage?
+ If 50% of all connections to a service result in abnormal
+ termination, that would be bad even under a non-attack scenario.
+
+ More accurate address verification: do a quota check before
+ reporting that a local(8) or virtual(8) recipient is deliverable.
+
+ Eliminate duplicate mail submission permission checks from
+ sendmail, so that they happen in postdrop only. Then, pass the
+ result through the postdrop-to-sendmail protocol. This requires
+ that postdrop reads all inputs before responding (the
+ local_login_sender_maps check depends on the envelope
+ sender). Then sendmail can save input to dead.letter (no setgid
+ privilege, but it would still have to use safe_open() to avoid
+ clobbering files).
+
+ Consider removing compat_level_from_numbers() and aliases,
+ because they are no longer used anywhere.
+
+ Allow '}' at the beginning of a line. This would make multi-line
+ configuration settings easier to enter. This may be true
+ for main.cf, master.cf and similar files (such as database
+ configuration files, but not necessarily elsewhere). So it
+ may have to be a readlline flag.
+
+ Understand what happens with DNSSEC related status fields
+ in posttls-finger when resolv.conf points to a host that
+ runs no DNS server.
+
+ Hardening the half-dane behavior: some sites may rely on
+ current behavior which allows original MX domain name for
+ certificate matches. Requires a new (compatibility) parameter
+ setting?
+
+ Code deduplication: migrate multi_server applications to
+ event_server, because the multi_server and event_server
+ skeletons are much more similar than other skeletons. In
+ addition to the default event_server accept() handler, also
+ register a read event callback for handling post_accept
+ events. But the currrent multi_server API fits typical usage
+ better.
+
+ When a secondary instance has no multi_instance_name set,
+ postmulti -i won't be able to find it.
+
+ nbbio: exercise the sanity checks with fake msg(3) functions.
+
+ optreset (bsd-ism) how badly do we need it?
+
+ transport policy protocol (clone of check_policy).
+
+ See also postscreen event-driven client for policy delegation
+ below.
+
+ smtp_line_length_limit can insert a line break in the middle
+ of a multi-byte character (which is not necessarily UTF-8,
+ so we can't simply look at the 8th bit). Also, note that a
+ multi-byte character may span queue file record boundaries,
+ for example if line_length_limit == smtp_line_length_limit.
+ The only way to fix this is to make the smtp_text_out()
+ routine aware of every possible multi-byte encoding.
+
+ Replace ad-hoc code for pipe(8) flags handling, with
+ infrastructure that was built for smtp(8).
+
+ Move map descriptions from postconf(1) to DATABASE_README
+ and point there. The text in DATABASE_README is less complete
+ than that in postconf(1).
+
+ make tls_pre_jail_init() safe by design for use in programs
+ that implement both clients and servers.
+
+ In smtpd(8) and postscreen(8), set the ehlo_discard_mask
+ to ~0 so that STARTTLS, BDAT, DSN, etc. work only for clients
+ that send EHLO.
+
+ Wordsmithing: "replace by X" -> "replace with X" unless X
+ is "responsible" for making the substitution.
+
+ In postscreen, don't fork after 'postfix reload' when
+ psc_check_queue_length (and psc_post_queue_length?) is zero.
+
+ After I/O error, store errno in VSTREAM object before errno
+ may be overwritten.
+
+ Add some tips for logging from container:
+ https://www.projectatomic.io/blog/2016/10/playing-with-docker-logging/;
+ syslog_name = $myhostname/postfix; mkdir queue and data
+ dir; postfix check to create queue subdirectories.
+
+ Add postwhite as a postscreen-related project.
+ https://github.com/stevejenkins/postwhite/blob/master/README.md
+
+ XFORWARD attributes in policy protocol?
+
+ Document postsrsd and postforward for srs-ifying. Would
+ more fine-grained smtp_generic_maps support help?
+
+ Decide whether to deprecate database configuration pathnames
+ that start with ".", for example, ldap:./file/name. These forms
+ are documented for ldap:, memcache:, mysql:, pgsql:, and sqlite:
+ maps. Postfix daemon processes will look up files relative to the
+ queue directory, but with postmap command-line processes it would
+ be more natural to interpret relative pathnames relative to the
+ current directory of the calling process (it would be a surprise
+ if "postmap hash:./foo" would access "/var/spool/postfix/foo",
+ or if "postmap hash:foo" and or "postmap hash:./foo" would access
+ different files).
+
+ Convert postalias(1) to store external-form keys, and convert
+ aliases(5) to perform external-first lookup with fallback to
+ internal form, to make it consistent with the rest of Postfix.
+ In several years we may remove the internal-form fallbacks
+ with a compatibility_level safety net.
+
+ In the bounce daemon, set util_utf8_enable if returning an
+ SMTPUTF8 message. This is wrong; if SMTPUTF8 is disabled,
+ then Postfix must not turn it on.
+
+ Add a header_body_checks extension callback in smtp_proto.c
+ that implements the PASS action.
+
+ Propagate SMTPD_PEER_CODE_XXX from smtpd(8) to cleanup(8),
+ so that {client_resolve} and {_} produce consistent results.
+
+ NO_IP_CYRUS_SASL_AUTH should be a main.cf parameter.
+
+ Modeline support in config files to enable/disable trailing
+ #comment, and to give hints about how to handle an LHS or
+ RHS. This will not preserve trailing comments in lines that
+ are modified with "postconf -e" and the like.
+
+ Maintainability: replace lengthy libmilter-API argument lists
+ with named parameters, as with the libtls API.
+
+ Fix buflen integer overflow detection in dict*sql.c.
+
+ Fix "make test" bitrot.
+
+ Move DNS-based tests from porcupine.org to postfix.org, or use
+ a mock DNS library (a library that presents the same API as the
+ real library, but that produces canned responses).
+
+ Document dns_ncache_ttl_fix_enable use case in POSTSCREEN_README
+ and RELEASE_NOTES.
+
+ Remove this file from the stable release.
+
+ Things to do after the stable release:
+
+ Specify WARN_UNUSED_RESULT for all library functions that
+ pass, deliver, bounce or defer a delivery request.
+
+ Invent some kind of type-checking wrappers for htable(3),
+ ctable(3) and other modules that take and return a void*
+ pointer. We already did that for variadic functions.
+
+ TLS certificate provenance: indicate whether a subject
+ name/issuer are verified or not (for example, change the
+ attribute name to unverified_ccert_subject etc.). This is
+ relevant only for fingerprint-based authentication including
+ DANE, and affects logging, SMTPD policy, and Milters.
+
+ Generalize the daemon '-S' stand-alone mode, so that it can
+ be used with custom configuration settings for request/reply
+ regression testing. This would use the existing "-o name=value"
+ support to override parameters. For example, queue_directory
+ would point to a directory with sockets for fake versions of
+ Postfix-internal services.
+
+ Update the list of Sendmail macros that Postfix can send
+ to Milters (auth_ssf and TLS-related).
+
+ Update smtpd command count when rejecting or skipping input
+ before command-table lookup. But then we need to count
+ commands that are rejected (malformed UTF-8, tokenizer
+ error, forbidden command), or skipped (noop).
+
+ What is the best place to detect spaces in pathnames during
+ installation/upgrade/packaging? postfix-install for early
+ warning, and post-install as a safety net?
+
+ When the service basename differs from the program file
+ basename, either prepend the service name to the syslogname (as
+ if syslog_name=postfix/service/program), or prepend the service
+ name to the process name (perhaps too confusing). The service
+ indication is desirable for mail delivery transports (smtp
+ versus relay) as it identifies what scheduler parameters are
+ in effect, but it is also desirable for mail receiving services
+ (smtp versus submission verus smtps as configured in the stock
+ master.cf file). This requires exceptions for some program names
+ (exclude smtpd to avoid logging postfix/smtp/smtpd which could
+ result in more confusion, and maybe other program names).
+
+ UTF8 DNS[BW]L domain name.
+
+ Consolidate maps flags in mail_params.h instead of having
+ multiple copies scattered across programs.
+
+ Try to allow UTF-8 myhostname/mydomain, at least in bounce
+ template expansion.
+
+ In the SMTP server, do not issue an enhanced status code when
+ rejecting a connection before the HELO handshake is completed.
+
+ Maybe don't whitelist a client that has maxed out its
+ per-MTA connection count limit.
+
+ Inline support for pcre:{/pattern/=action, ...} and ditto
+ support for regexp: and cidr: tables. Factor out and reuse
+ code that already exists in inline: and other tables.
+
+ Log command=good/bad statistics in postscreen?
+
+ smtpd_checks tests either must use a DNS dummy resolver
+ (override the res_search API) or all names must be under
+ test.postfix.org (but that does not work for address->name
+ lookups, and cannot simulate some errors).
+
+ Reporting the original Message-ID in a bounce message
+ In-Reply-To: or References: header. In the cleanup daemon,
+ grab a copy of the Message-ID and export it along with other
+ header-extracted information at the top of the "extracted"
+ queue file segment. In the queue manager, extract this
+ along with other header-extracted information, and forward
+ the Message-ID in the bounce server notification request.
+
+ Clobber ORCPT when sender is owner-mumble?
+
+ Add milter_mumble_macros to the list of per-macro features.
+
+ The pickup daemon logs warnings only when the cleanup daemon
+ dit not provide a "reason" attribute. Is this logic right?
+
+ up-convert myhostname to UTF-8 in MIME boundary strings?
+
+ Eliminate code duplication between pcf_print_master_field()
+ and pcf_print_master_entry().
+
+ Error reporting: see if pcf_check_master_entry() and children
+ can return error descriptions instead of terminating with
+ a fatal error.
+
+ Add a switch to consider postscreen deep protocol tests as
+ "completed" when receiving "RSET" after "RCPT TO" and the
+ session has passed all tests up to that point. RSET becomes
+ like QUIT except perhaps that it does not hang up.
+
+ apipe: map, splits results into address lists and performs
+ lookups for the invidual addresses, converting back and
+ forth between external and internal forms.
+
+ Clarify that receive_override_options have no effect with
+ smtpd_proxy_filter.
+
+ Document the relative order of header_checks, address
+ rewriting, milters.
+
+ NOT: Table-driven case folding and case-insensitive string
+ comparison specifically for UTF-8. Use libicu functions
+ instead.
+
+ When downgrading message/global to 7bit, is quoted-printable
+ the appropriate encoding? Should it be base64?
+
+ Should we encode headers with RFC 2047, when that is the
+ only reason that Postfix cannot deliver to a non-UTF8SMTP
+ server? Probably not in the general case. What about
+ Postfix as a gateway server that converts UTF8SMTP
+ for delivery to non-UTF8SMTP environments?
+
+ Document and test restriction_classes example for
+ smtpd_policy_service_default_action.
+
+ Don't accept AUTH or other features that are not announced
+ in the EHLO response.
+
+ Suggested at Mailserver conference: Postscreen RDNS-based
+ reputation (but this makes postscreen performance highly
+ unpredicable because it introduces a dependency on random
+ DNS servers).
+
+ Suggested at Mailserver conference: a way to select a
+ specific field in a table, presumably as the result value.
+ This may be done with a filtermap{i,j,...}: table that propagates
+ only the specified field(s).
+
+ Discourage the use of "after 220" tests in POSTSCREEN_README
+ and the documentation of individual parameter settings.
+
+ To un-break "make tests" under src/smtpd, make tests
+ independent from the DNS and native routines for host
+ name/address lookup.
+
+ Make been_here flag BH_FLAG_FOLD configurable for masochists.
+
+ Replace some redundant TLS_README sections with pointers
+ to FORWARD_SECRECY_README.
+
+ Move html/index.html source to proto/.
+
+ How hard is it to follow canonical or virtual mapping
+ for the purpose of address validation? We must never
+ reject a valid address.
+
+ Preserve case in smtpd_resolve_addr() and add a structure
+ member for the case-folded address. IIRC some Milter macro
+ needs to show the unfolded address.
+
+ Per SASL account rate limits. This requires new infrastructure
+ that maintains stats by SASL account instead of client IP
+ address.
+
+ Watchdog timer in postmap/postalias.
+
+ Begin code revision, after DANE support stabilizes. This
+ should be one pass that changes only names and no code.
+
+ recipient_delimiters = $recipient_delimiter for BC
+
+ All source code must specify its original author and
+ license statement. Some code modules specify Lutz Jaenicke
+ as the original author and fall under his liberal license.
+ Code that is added to such a module has the same license
+ (or at least something that is not more restrictive). Code
+ modules without input from Lutz Jaenicke must state its
+ original author and license (preferably no more restrictive
+ than Postfix's own license). Currently, too many files list
+ Wietse as the original author, and Lutz Jaenicke's license,
+ which is wrong.
+
+ We have smtp_host_lookup, smtp_dns_resolver_options, and
+ now smtp_dns_support_level. Of these, smtp_dns_resolver_options
+ is orthogonal but the rest has overlap.
+
+ There needs to be support for automatic migration from the
+ deprecated disable_dns_lookups feature to the preferred
+ smtp_dns_support_level feature. This support needs to exist
+ for several releases before the deprecated feature can be
+ removed.
+
+ End code revision, after DANE support stabilizes.
+
+ It would be nice if "bare username" lookup is not hard-coded
+ for domains in the local address class.
+
+ Don't forget Apple's code donation for fetching mail from
+ IMAP server.
+
+ Should postconf -o refuse to work without the -x option?
+
+ Make 30s caching (feature 20070414) configurable, such that
+ 0 means no caching.
+
+ Make errno white/blacklist for getpwnam_r etc. and mailbox
+ write errors.
+
+ smtpd_muble_restrictions rule names are case-insensitive.
+ restriction_classes values are case-sensitive but should
+ be case-insensitive for consistency with smtpd_muble_restrictions.
+
+ Make "rename" the default when postmapping a DB file
+ (later: use copy+rename for postmap -i, postmap -d).
+
+ Service-name parameters aren't documented in daemon manpages.
+
+ When faking up the DSN ORCPT, don't send bare usernames
+ from local command-line submission.
+
+ lmtp_assume_final is broken. A 2XX response does not imply
+ final delivery. The Sieve language implements accept-then-bounce.
+
+ postscreen event-driven plug-in interface to send out a
+ query in parallel with the Pregreet and DNSBL tests, using
+ a simplified version of the policy delegation protocol.
+
+ Parallelized queue preprocessing: rip out the queue manager
+ code to read queue files and resolve recipients, and run
+ it in parallel processes. The queue manager then processes
+ their results as they become available. This would eliminate
+ the qmgr<->trivial-rewrite bottleneck. This can also eliminate
+ much of the scheduling disadvantage of a single queue manager
+ compared to hundreds of mail receiving or sending processes
+ (especially if there is a way to scan the queue in parallel).
+
+ Memory pools for same-type memory objects. This can be
+ used to either increase memory locality for frequently-allocated
+ objects (MRU allocation) or to make use-after-free bugs
+ more detectable (use LRU allocation and wipe the object
+ immediately after free(). Finally, same-type memory pools
+ prevent object type errors with use-after-free bugs.
+
+ "no-cache" option for selected postscreen tests?
+
+ Need a new DICT flag to indicate that a map handle supports
+ locking. If it doesn't (as with memcache or proxymap
+ handles), then postscreen etc. don't need to close a cache
+ file after "postfix reload". After a fork() it is OK to
+ keep using a memcache or proxymap handle, because the parent
+ exits immediately. For this to work, the memcache client
+ needs to propagate the flag from a persistent backup map,
+ but the proxymap protocol should not propagate this to the
+ client.
+
+ Different TTL values for different DNSBL sources?
+
+ Replace master(8) SIGHUP by very simple socket protocol to
+ allow reload of a specific service.
+
+ postscreen: in the dummy SMTP engine, log the protocol state
+ at time of violation (like smtpd, set state->where initially
+ to CONNECT, then update it with the name of the last "known"
+ command, or set it to "unimplemented").
+
+ The discussion of postscreen cache configuration is in the
+ wrong place (how whitelisting works). Move it to the section
+ about configuring postscreen.
+
+ Before proxymap can be exposed to the network (primarily
+ to share postscreen or verify caches), need to enforce
+ limits on attribute string name and value length in IPC
+ protocols. 10-20KB seems OK. We need to enforce content
+ sanity checks (for example, no control characters; Postfix
+ does not pass around multi-line data in table lookups). The
+ VSTREAM library already supports read/write deadlines. We
+ need to use attack-resistant code for numeric conversion.
+
+ move flush_init() etc. from defer service clients to the
+ bounce daemon? Postfix works best when work can be spread
+ out over many clients, instead of over a few servers.
+
+ multi_connect() function that takes a list of inet:host:port
+ and/or unix:pathname specs, with an explicit "inet" prefix
+ argument to handle applications that use host:port only.
+ This will simplify multi-host implementation for memcache
+ client, dovecot client, and other.
+
+ dict_memcache: treat "bad" key as cache miss, i.e. read/write
+ the backup database as if the cache did not exist. This
+ does not help because most Postfix maps (virtual, canonical,
+ access, transport, ...) also don't support spaces in keys.
+
+ postscreen: keep the cache open after "postfix reload" when
+ it is remote (type memcache: or proxy:). This does not work
+ because memcache can use a non-proxied file as backup).
+
+ What is the feasibility of adding an mta_name (personality)
+ attribute that is propagated via queue files and delivery
+ agent requests? It would default to myhostname.
+
+ Major performance improvement opportunity (that is until
+ everyone runs Postfix queues on SSDs). Investigate the
+ viability of a daemon that produces incoming and postdrop
+ queue files on request (in reality it would maintain a
+ limited queue of "spare" files). Central queue file allocation
+ reduces the I/O performance disadvantage that qmgr has when
+ 100 smtpd processes are receiving mail, or when lots of
+ mail is submitted with the sendmail command line. When an
+ smtpd process accepts MAIL FROM, a cleanup daemon requests
+ a queue file and receives a queue ID + file handle from the
+ queue file daemon. If the queue file daemon is down, the
+ cleanup daemon creates the file itself like it does now;
+ this can be hidden in the mail_stream library module. If
+ the mail transaction is aborted, then the cleanup daemon
+ gives the queue file back to the queue file daemon's "spare"
+ file pool, saving most of the overhead of creating and
+ deleting a queue file (the file would still need to be
+ renamed at the start of the next mail transaction). If the
+ cleanup daemon is unable to give a file back, then it can
+ delete the file like it does now; this can be hidden in the
+ mail_stream library module. The whole thing can be
+ transparently added to Postfix by adding calls to a
+ queue-file-service client to the mail_queue_enter() and
+ mail_queue_remove() library routines. Other advantages:
+ 1) negligible performance hit when queue file allocation
+ happens earlier, so that logging and milters have a queue
+ ID for the whole transaction not just the first valid
+ recipient; 2) by not removing every queue files we get most
+ of the performance gain of a queue based on append/truncate
+ instead of the much more expensive create/delete.
+
+ Investigate viability of Sendmail dns maps.
+
+ Make the rules for how to use close-on-exec more explicit.
+
+ Provide separate timeout control for dict_proxy client,
+ rewrite client, resolve client, cleanup client, and so on.
+ Perhaps a timeout argument to the mail_connect() routines.
+
+ Trick from amavisd: save listen socket/fifo/etc state, clear
+ their close-on-exec flags, exec the same program file to
+ re-initialize (with saved socket state on command line or
+ in environment), then restore the listen socket/fifo/etc
+ close-on-exec flags. This could be a way to mitigate the
+ impact of memory/file leaks, and to implement "postfix
+ reload" support for master(8) features that currently don't
+ support this.
+
+ Sub-second time resolution. The first benefit is to make
+ per-destination rate delays more usable. Other applications
+ will come up once the support exists. The straightforward
+ approach is to represent all time intervals in milliseconds,
+ and to update all code that makes system calls with a time
+ argument (as well as the compiled-in upper and lower time
+ parameter bounds, which are currently in seconds).
+ Unfortunately, that limits he maximum time interval to less
+ than 25 days on 32-bit systems, and is likely to break
+ compatibility (for starters, it cannot even deal with the
+ compiled-in 100d upper bound on the queue file lifetime).
+ A second option is to have a "compatibility" time base
+ switch between milliseconds and seconds; this means extra
+ changes to all code that makes system calls with a time
+ argument, and the way that the compiled-in upper and lower
+ bounds are specified. Some of this can be encapsulated in
+ macros like time_to_sec(t), time_to_msec(t) and sec_to_time(t).
+ Finally, it is relatively easy to replace the events(3)
+ interface to use "double" for the time delay arguments, but
+ it is a major pain to convert all main.cf time parameters
+ into doubles (converting only some leads to a documentation
+ nightmare).
+
+ Address verify cache: allow a negative cache "refresh"
+ result to purge a "positive" cache entry in some safe manner.
+ Currently, the negative cache "refresh" result is discarded,
+ address verify cache lookup returns OK, and each lookup
+ forces a "refresh" probe until the entry expires.
+
+ Some Sendmail configurations trigger sub-optimal behavior
+ when the postscreen_whitelist_interfaces parameter lists
+ primary MX addresses only. When postscreen's "deep protocol
+ tests" are successful on the primary MX address (i.e. they
+ result in 4XX responses to RCPT TO), some Sendmail
+ configurations keep the primary MX connection open until
+ AFTER they finish talking to the backup MX address. The
+ problem is that the backup connection runs into a WHITELIST
+ VETO condition because the whitelisting database has not
+ yet been updated with the PASS NEW result for the primary
+ MX connection. Unfortunately postscreen can't update the
+ whitelisting database before the primary MX connection is
+ closed, because a client may still make a mistake.
+
+ In the SMTP server, check if the connection is closed before
+ replying to ".", and discard the message if the reply can't
+ be sent. This reduces the time window for RFC 1047 message
+ duplication, and may even prevent the delivery of some spam.
+ http://www.exim.org/lurker/message/20070416.103159.9d5ff0ce.en.html
+ This requires splitting the SMTP server's commit operation
+ into two operations: first, a tentative commit operation
+ that performs most of the I/O and processing in milters and
+ in the cleanup server; second, a final commit operation
+ that is executed only if the remote SMTP client hasn't hung
+ up in the mean time. Unfortunately, SMTP-based before-queue
+ content filters don't support a tentative commit operation.
+
+ Find out how to reproduce Berkeley DB bogus ENOENT errors.
+ postscreen does not log this with Berkeley DB 1 (FreeBSD
+ 4..8), 4.7.25 (Ubuntu 9.04) and 4.8.24 (Ubuntu 10.04).
+
+ postconf command-line option to show the compile-time
+ settings (CCARGS, AUXLIBS) in case binary packages
+ don't install the makedefs.out file.
+
+ events.c: cache the side effects of file descriptor event
+ enable/disable operations in user space, and do bulk kernel
+ updates at event_loop() time. This can eliminate costly
+ system calls with successive event disable/enable operations
+ on the same file descriptor. This can also eliminate the
+ need for tricky code that tries to avoid the expense of
+ successive disable/enable operations. Such code is likely
+ to introduce bugs.
+
+ When does it pay off to send domains in the active queue
+ to a DNS prefetch daemon? Could this generalize to a dynamic
+ transport map that piggy-backs domains with the same MX
+ host into the same mail delivery transaction?
+
+ tlsproxy(8) should receive TLS preferences from postscreen(8)
+ and smtpd(8), instead of reading them from main.cf. This
+ means that many tlsproxy_ parameters become postscreen_
+ parameters, and that tls_server_init() parameters move to
+ to tls_server_start(). That is a significant API change.
+ It also means tlsproxy can't open all files before chroot().
+
+ anvil rate limit for sasl_username.
+
+ Encapsulate nbbio buffer access and update by tlsproxy.
+
+ Full-duplex support for tlsproxy(8). This requires updating
+ events(3) and nbbio(3).
+
+ Register automagic destructor for object attached to VSTREAM.
+
+ Use different ipc time limits for email message transactions
+ (smtpd, pickup)->cleanup and for quick query/reply transactions
+ such as address rewriting/resolution. Beware of large time
+ limits for local or virtual alias expansion.
+
+ permit_tempfail_action (default: defer_if_reject) to be
+ used as the default value for dnswl_tempfail_action and
+ rhswl_tempfail_action. Steal liberally from the code that
+ implements unverified_recipient_tempfail_action etc.
+
+ Support filtering of messages that are generated by Postfix:
+ This would apply to postmaster notices and bounce messages
+ (DKIM), and address verification (BATV).
+
+ Consistency: in postconf.proto make <dt>..</dt> tags bold.
+
+ Would it help if there were different cleanup_service
+ parameter names for different message paths? smtpd(8) uses
+ the same cleanup_service value for receiving remote mail
+ and for submitting postmaster problem reports. Do we need
+ separate mumble_cleanup_service_name parameters for "inject",
+ "notify" and "forward" (with backwards compatible defaults)?
+
+ IF/ENDIF support for CIDR tables.
+
+ Need a regular expression table to translate address
+ verification responses into hard/soft/accept reply codes.
+
+ Is there a way to make sendmail -V work after local alias
+ expansion? Majordomo-like mailing lists would benefit from
+ this; the example in VERP_README does not work in the general
+ case.
+
+ When an alias is a member of an :include: list with owner-
+ alias, local(8) needs an option to deliver alias or alias->user
+ indirectly. What happens when an :include: list with owner-
+ alias includes another list?
+
+ Don't allow empty result values in pcre and regexp maps.
+ Postfix doesn't allow them anywhere else (check this).
+
+ Make PCRE_MAX_CAPTURE configurable.
+
+ Add some checks for tokens starting with #. A challenge
+ is to report sensible context from the guts of some low-level
+ parser, without introducing a great deal of clumsiness.
+
+ Add sendmail macros for {verify} and maybe other TLS info.
+
+ Find out if we are doing the correct thing by looking at
+ state->milter_reject_text when expanding {rcpt_addr} or
+ {rcpt_host}.
+
+ Find out why post_mail() etc. block when the qmgr fifo is
+ full (answer: trigger_timeout). How can this cause delays
+ in the queue manager? When a recipient bounces during
+ (transport, nexthop, address) resolution, it is redirected
+ to the error or retry mailer; and bounce-after-delivery is
+ asynchrounous so it can't block the queue manager, either.
+
+ How to ensure that proxy_read_maps is processed after all
+ its dependencies are initialized, or just bite the bullet
+ and rewrite the parameter initialization code.
+
+ The cleanup virtual alias expansion limit does not really
+ deliver on its promises. 1) It promises to truncate the
+ result without aborting delivery, which would be undesirable
+ anyway, but that is not what it does, so that is good. 2)
+ It keeps all the recipients from multi-recipient database
+ lookup, then terminates further recursion when the result
+ exceeds the expansion limit. This behavior achieves the
+ original goal that all things shall have a finite size (even
+ though but we don'really care how large they are) but may
+ result in surprises when recipients are listed in virtual
+ alias domains or need expansion for other reasons. In a
+ phone call with Victor, a reasonable way out is to set the
+ limit to some large number (100000) and abort delivery when
+ the result exceeds the limit.
+
+ Should the postscreen save permanent white/black list lookup
+ results to the temporary cache, and query the temporary
+ cache first? Skipping white/black list lookups will speed
+ up the handling of "good" clients without a permanent
+ whitelist entry. Of course, this means that updates to the
+ white/black lists do not immediately take effect. Workarounds:
+ 1) use a shorter temporary cache TTL for clients on the
+ permanent black/white lists; 2) ignore cached white/black
+ list lookup results after "postfix reload"; 2) adjust the
+ logging, for example "WHITELISTED address (cached)" and
+ "BLACKLISTED address (cached)" to eliminate surprises.
+ Comparing the cache entry time with the white/blacklist
+ file modification time is not foolproof: for example, pcre
+ or CIDR tables are read only once.
+
+ It would be nice if the generic dict_cache(3) cache manager
+ could postpone process suicide until cache cleanup is
+ completed (but that is not possible when postscreen forks
+ into the background to finish already-accepted connections,
+ and it is not desirable when a host is being shut down).
+
+ When postscreen drops a connection, a 521 "greeting" should
+ be of the form "521 servername..." and not have an enhanced
+ status code. The "521 5.7.1" form can be used after EHLO.
+ Of course no spammer is going to complain about Postfix
+ SMTP compliance.
+
+ Find a place to document all the mail routing mechanisms
+ in one place so people can figure out how Postfix works.
+
+ The access map BCC action is marked "not stable", perhaps
+ because people would also expect BCC actions in header/body_checks.
+ How much would it take to make the queue file editing code
+ generally usable?
+
+ Move smtpd_command_filter into smtpd_chat_query() and update
+ the session transcript (see smtp_chat_reply() for an example).
+
+ SMTP connection caching without storing connections, to
+ improve TLS mail delivery performance.
+
+ Should not milter8_mail_event() unset the "hold" default
+ reply? Better, the default reply should not be used for
+ this purpose.
+
+ Don't send MASTER_STAT_TAKEN/MASTER_STAT_AVAIL when a server
+ runs with process limit of 1. But this means the master
+ never learns that the process is successful and will always
+ pause $service_throttle_time before restarting a failed service.
+
+ Don't bother maintaining a per-service lockfile when a
+ server runs with process limit of 1. The purpose of the
+ lockfile is to avoid thundering herd problems when the kernel
+ wakes up multiple processes for each new client connection.
+
+ Implement PREPEND action for milter_header_checks. Save the
+ to-be-prepended text to buffer, then emit it along with the
+ new header.
+
+ Fix the header_body_checks API, so that the name of the map
+ class (e.g. milter_header_checks) is available for logging.
+
+ Fix the mime_state and header_body_checks APIs, so that
+ they use VSTRINGs. This simplifies REPLACE actions.
+
+ Update FILTER_README for multi-instance support, and rename
+ the old document to FILTER_LEGACY_README.
+
+ Need to sign delivery status notifications, to avoid surprises
+ when eventually people start enforcing DKIM etc. signatures.
+
+ Either document or remove the internal_mail_filter_classes
+ feature (it's disabled by default).
+
+ Make the "unknown recipient" test configurable as
+ first|last|never, with "yes"=="last" for backwards
+ compatibility. The "first" setting is good for performance
+ (stress=yes) when all users are defined in local files; but
+ it may perform worse when users are in networked tables.
+
+ Cleanup: make DNSBL query format configurable beyond the
+ client's reversed IP address.
+
+ With 'final delivery' in the LMTP client, need an option
+ to also add delivered-to and other pipe(8) features. This
+ requires making mail_copy() functionality available in
+ non-mailbox context.
+
+ Cleanup: modernize the "add missing From: header" code, to
+ ``phrase <addr>'' form. Most likely, quote the entire phrase
+ if it contains any text that is special, then rfc822_externalize
+ the whole thing.
+
+ SMTP server: make the server_addr and server_port available
+ to policy server, Dovecot, and perhaps Milters.
+
+ Med: local and remote source port and IP address for smtpd
+ policy hook.
+
+ Maybe change maps_rbl_reject_code default to 521, and
+ update wording in STRESS_README.
+
+ Encapsulate time_t comparisons so that they can be made
+ system dependent (use difftime() where available).
+
+ Encapsulate time_t conversions (e.g. REC_TYPE_TIME) so that
+ they can be made system dependent.
+
+ Plan for time_t larger than long, or wait for LP64 to
+ dominate the world?
+
+ Make "AUTH=<>" appendage to MAIL FROM configurable, enabled
+ by default.
+
+ To support ternary operator without a huge parsing effort,
+ consider ${value?{xxx}:{yyy}} where ${name} is existing
+ syntax, and where ?{text} and :{text} are new syntax that
+ is unlikely to break existing configurations. Or perhaps
+ it's just too ugly.
+
+ Write delivery rate delay example (which _README?) and auth
+ failure cache example (SASL_README). Then include them in
+ SOHO_README.
+
+ Look for alternatives for the use of non_smtpd_milters.
+ This involves some way to force local submissions to go
+ through a local SMTP client and server, without triggering
+ "mail loops back to myself" false alarms. The advantage is
+ that it makes smtpd_mumble_restrictions available for local
+ and remote mail; the disadvantage is that it makes local
+ submissions more dependent on networking. One possibility
+ is to use "pickup -o content_filter=smtp:127.0.0.1:10025",
+ or a dedicated SMTP client/server on UNIX-domain sockets;
+ we could also decide to always suppress "mail loop" detection
+ for loopback connections. Another option is to have the
+ pickup or cleanup server drive an SMTP client directly;
+ this would require extension of the mail_stream() interface,
+ plus a way to handle bounced/deferred recipients intelligently,
+ but it would be at odds with Postfix design where delivery
+ agents access queue files directly; exposing delivery agents
+ to raw queue files violates another Postfix design principle.
+
+ Consolidate duplicated code in *_server_accept_{pass,inet}().
+
+ Consolidate duplicated code in {inet,unix,upass}_trigger.c.
+
+ In the SMTP client, handle 421 replies in smtp_loop() by
+ having the input function raise a flag after detecting 421
+ (kill connection caching and be sure to do the right thing
+ with RSET probes), leave the smtp_loop() per-command reply
+ handlers unchanged, and have the smtp_loop() reader loop
+ bail out with smtp_site_fail("server disconnected after
+ %s", where), but only in the case that it isn't already in
+ the final state. But first we need to clean up the handling
+ of do/don't cache, expired, bad and dead sessions.
+
+ Combine smtpd_peer.c and qmqpd_peer.c into a single function
+ that produces a client context object, and provide attribute
+ print/scan routines that pass these client context objects
+ around. With this, we no longer have to update multiple
+ pieces of code when a client attribute is added. Ditto for
+ SASL and TLS context.
+
+ Don't log "warning: XXXXX: undeliverable postmaster
+ notification discarded" for spam from outside.
+
+ Really need a cleanup driver that allows testing against
+ Milter applications instead of synthetic events. This would
+ have to provide stubs for clients that talk to Postfix
+ daemon processes. See if this approach can also be used for
+ other daemons.
+
+ smtpd(8) exempts $address_verify_sender from access controls,
+ but it doesn't know whether cleanup(8) or delivery agents
+ modify the sender. Would it be possible to "calibrate" this
+ exemption, perhaps by having delivery agents pass the probe
+ sender to the verify server, keeping in mind that the probe
+ sender may differ per delivery agent due to output rewriting.
+
+ Update attr_print/scan() so they can send/receive file
+ descriptors. This simplifies kludgy code in many daemons.
+
+ Would there be a problem adding $smtpd_mumble_restrictions
+ and $smtpd_sender_login_maps to the default proxy_read_maps
+ settings?
+
+ Remove defer(8) and trace(8) references and man pages. These
+ are services not program names. On the other hand we have
+ man pages for lmtp(8) and smtp(8), but not for relay(8).
+ Likewise, retry(8) does not have a man page.
+
+ Bind all deliveries to the same local delivery process,
+ making Postfix perform as poorly as monolithic mailers, but
+ giving a possibility to eliminate duplicate deliveries.
+
+ Maybe declare loop when resolve_local(mxhost) is true?
+
+ Update message content length when adding/removing headers.
+
+ Need scache size limit.
+
+ REDIRECT should override original recipient info, and
+ probably override DSN as well.
+
+ Update FILTER_README with mailing list suggestions to tag
+ with a badness indicator and then filter down-stream.
+
+ Make null local-part handling configurable: either expand
+ into mailer-daemon (current behavior) or disallow (strict
+ behavior, currently implemented only in the SMTP server).
+
+ Add M flag (enable multi-recipient delivery) to pipe daemon.
+
+ The usage of TLScontext->cache_type is unclear. It specifies
+ a TLS session cache type (smtpd, smtp, or lmtp), but it is
+ sometimes used as an indicator that TLS session caching is
+ unavailable. In reality, that decision is made by not
+ registering call-back functions for cache maintenance.
+
+ Postfix TLS library code should copy any strings that it
+ receives from the application, instead of passing them
+ around as pointers. TLScontext->cache_type is a case in
+ point.
+
+ Are transport:nexthop null fields the same as in the case
+ of default_transport etc. parameters?
+
+ Don't lose bits when converting st_dev into maildir file
+ name. It's 64 bits on Linux. Found with the BEAM source
+ code analyzer. Is this really a problem, or are they just
+ using 64 bits for upwards compatibility with LP64 systems?
+
+ Do or don't introduce unknown_reverse_client_reject_code.
+
+ Check that "UINT32 == unsigned int" choice is ok (i.e. LP64
+ UNIX).
+
+ Tempfail when a Milter application tries to negotiate content
+ access, while it is configured in an SMTP server that runs
+ before the smtpd_proxy filter.
+
+ Log DSN original recipient when rejecting mail.
+
+ Keep whitespace between label and ":"?
+
+ Make the map case folding/locking options configurable, if
+ not at run-time then at least at compile time so we get
+ consistent behavior across applications.
+
+ Investigate what it would take to eliminate oqmgr, and to
+ make the old behavior configurable in a unified queue
+ manager. This would shave another 2.7 KLOC from the source
+ footprint.
+
+ Document the case folding strategy for match_list like
+ features.
+
+ Eliminate the (incoming,deferred)->active rename operation.
+ This requires an in-memory hash of queue file names to avoid
+ duplicate open() operations.
+
+ Softbounce fallback-to-ISP for SOHO users. This heuristic
+ assumes that when direct-to-MX delivery fails with 5XX,
+ delivery via the ISP may still succeed. This could be
+ implemented by enabling soft bounces for destinations other
+ than the smtp_fallback_relay. So the only benefit of this
+ over the existing soft_bounce feature is that it has no
+ effect on smtp_fallback_relay deliveries.
+
+ Centralize main.cf parameter input so that defaults work
+ consistently. What about parameter names that are prefixed
+ with mail delivery transport names?
+
+ Fix default time unit handling so that we can have a default
+ bounce lifetime of $maximal_queue_lifetime, without causing
+ panics when a non-default maximal_queue_lifetime setting
+ includes no time unit.
+
+ After the 20051222 ISASCII paranoia, lowercase() lowercases
+ ASCII text only.
+
+ Privacy: remove local command/pathname details from remote
+ delivery status reports, and log them via local msg_warn().
+
+ Is it safe to cache a connection after it has been used for
+ more than some number of address verification probes?
+
+ Try to recognize that Resent- headers appear in blocks,
+ newest block first. But don't break on incorrect header
+ block organization.
+
+ Hard limits on cache sizes (anvil, specifically).
+
+ Laptop friendliness: make the qmgr remember when the next
+ deferred queue scan needs to be done, and have the pickup
+ server stat() the maildrop directory before searching it.
+
+ Low: replace_sender/replace_recipient actions in access
+ maps, so they can be used in policy servers?
+
+ Low: configurable order of local(8) delivery methods.
+
+ Med: smtp_connect_timeout_budget (default: 3x smtp_connect_timeout)
+ to limit the total time spent trying to connect.
+
+ Med: transform IPv4-in-IPv6 address literals to IPv4 form
+ when comparing against local IP addresses?
+
+ Med: transform IPv4-in-IPv6 address literals to IPv4 form
+ when eliminating MX mailer loops?
+
+ Med: Postfix requires [] around IPv6 address information
+ in match lists such as mynetworks, debug_peer_list etc.,
+ but the [] must not be specified in access(5) maps. Other
+ places don't care. For now, this gotcha is documented in
+ IPV6_README and in postconf(5) with each feature that may
+ use IPv6 address information. The general recommendation
+ is not to use [] unless absolutely necessary.
+
+ Med: the partial address matching of IPv6 addresses in
+ access(5) maps is a bit lame: it repeatedly truncates the
+ last ":octetpair" from the printable address representation
+ until a match is found or until truncation is no longer
+ possible. Since one or more ":" are usually omitted from
+ the printable IPv6 address representation, this does not
+ really try all the possibilities that one might expect to
+ be tried. For now, this gotcha is documented in access(5).
+
+ Low: reject HELO with any domain name or IP address that
+ this MTA is the final destination for.
+
+ Low: should the Delivered-To: test in local(8) be configurable?
+
+ Low: make mail_addr_find() lookup configurable.
+
+ Low: update events.c so that 1-second timer requests do not
+ suffer from rounding errors. This is needed for 1-second
+ SMTP session caching time limits. A 1-second interval would
+ become arbitrarily short when an event is scheduled just
+ before the current second rolls over.
+
+ Low: configurable internal/system locking method.
+
+ Low: add INSTALL section for pre-existing Postfix systems.
+
+ Low: add INSTALL section for pre-existing RPM Postfixes.
+
+ Low: disallow smtpd_recipient_limit < 100 (the RFC minimum).
+
+ Low: noise filter: allow smtp(8) to retry immediately if
+ all MXes return a quick ECONNRESET or 4xx reply during the
+ initial handshake. Retry once? How many times?
+
+ Low: make post-install a "postfix-only script" so it can
+ take data from the environment instead of main.cf.
+
+ Low: randomize deferred mail backoff.
+
+ Med: separate ulimit for delivery to command?
+
+ Med: postsuper -r should do something with recipients in
+ bounce logfiles, to make sure the sender will be notified.
+ To be perfectly safe, no process other than the queue manager
+ should move a queue file away from the active queue.
+
+ This could involve tagging a queue file, and use up another
+ permission bit (postsuper tags a "hot" file, qmgr requeues it).
+
+ Low: postsuper re-run after renaming files, but only a
+ limited number of times.
+
+ Low: smtp-source may block when sending large test messages.
+
+ Med: find a way to log the sender address when MAIL FROM
+ is rejected due to lack of disk space.
+
+ Low: revise other local delivery agent duplicate filters.
+
+ Low: all table lookups should consistently use internalized
+ (unquoted) or externalized (quoted) forms as lookup keys.
+ smtpd, qmgr, local, etc. use unquoted address forms as keys.
+ cleanup uses quoted forms.
+
+ Low: have a configurable list of errno values for mailbox
+ or maildir delivery that result in deferral rather than
+ bouncing mail. What about "killed by signal" exits?
+
+ Low: after reorganizing configuration parameters, add flags
+ to all parameters whose value can be read from file.
+
+ Medium: need in-process caching for map lookups. LDAP servers
+ seem to need this in particular. Need a way to expire cached
+ results that are too old.
+
+ Low: generic showq protocol, to allow for more intelligent
+ processing than just mailq. Maybe marry this with postsuper.
+
+ Low: default domain for appending to unqualified recipients,
+ so that unqualified names can be delivered locally.
+
+ Low: The $process_id_directory setting is not used anywhere
+ in Postfix. Problem reported by Michael Smith, texas.net.
+ This should be documented, or better, the code should warn
+ about attempts to set read-only parameters.
+
+ Low: while converting 8bit text to quoted-printable, perhaps
+ use =46rom to avoid having to produce >From when delivering
+ to mailbox.
+
+ virtual_mailbox_path expression like forward_path, so that
+ people can specify prefix and suffix.