head 1.1; branch 1.1.1; access; symbols netbsd-11-0-RC4:1.1.1.1.2.2 netbsd-11:1.1.1.1.0.2 PFIX-3-11-2:1.1.1.1 VENEMA:1.1.1; locks; strict; comment @# @; 1.1 date 2026.05.09.18.39.10; author christos; state Exp; branches 1.1.1.1; next ; commitid mtbvlXzNqJaszaFG; 1.1.1.1 date 2026.05.09.18.39.10; author christos; state Exp; branches 1.1.1.1.2.1; next ; commitid mtbvlXzNqJaszaFG; 1.1.1.1.2.1 date 2026.05.09.18.39.10; author martin; state dead; branches; next 1.1.1.1.2.2; commitid 2QeqaJm8KrXk4qFG; 1.1.1.1.2.2 date 2026.05.11.17.13.37; author martin; state Exp; branches; next ; commitid 2QeqaJm8KrXk4qFG; desc @@ 1.1 log @Initial revision @ text @ Postfix REQUIRETLS Support

Postfix REQUIRETLS Support

Purpose of this document
Introduction
REQUIRETLS for a perimeter MTA
An experiment: testing REQUIRETLS support
Requesting REQUIRETLS without SMTP
Non-delivery notifications
REQUIRETLS quick summary
Credits

Purpose of this document

This document covers Postfix configuration for the REQUIRETLS extension. The purpose of these settings is to make REQUIRETLS support usable in an existing environment where REQUIRETLS support is still uncommon, with a path towards a future with REQUIRETLS.

Introduction

The REQUIRETLS extension in ESMTP is defined in RFC 8689. When a sender requests REQUIRETLS. the message must be sent only over strongly-authenticated SMTP or LMTP connections.

Specifically:

Every server in the forward path to the final destination must announce REQUIRETLS support.

Challenge: as of 2025, only a few servers implement REQUIRETLS.
Every server in the forward path must be looked up securely (for example, with DNSSEC or HTTPS).
Every server certificate in the forward path must be verified. In practice, this involves DANE (+DNSSEC) or MTA-STS; custom configuration would not scale.

Challenge: as of 2025, many domains do not publish a DANE or MTA-STS policy.
A message with REQUIRETLS must be returned to the sender if any of the above requirements is not satisfied (no STARTTLS support, no secure server lookup, no trusted or no matching server certificate, or no server that announces REQUIRETLS support).

For more background information, see the REQUIRETLS quick summary below.

REQUIRETLS for a perimeter MTA

In this text, a perimeter MTA is a mail system that operates on the boundary of an administrative domain. It receives email messages for the domain, and/or sends email messages on behalf of the domain.

Receiving inbound messages with REQUIRETLS requests

Postfix has one global parameter setting that controls REQUIRETLS support in all Postfix processes. The default setting is:

/etc/postfix/main.cf:
    requiretls_enable = yes

With this, the Postfix SMTP server will announce REQUIRETLS support, and more importantly, will receive messages from senders that for some reason request REQUIRETLS support -- messages that you would otherwise not receive, assuming that the domain already publishes a valid DANE and/or STS policy.

If all you need is to receive messages with REQUIRETLS, and you do not insist on enforcing REQUIRETLS when sending or forwarding messages, then you can stop reading this document after adding the additional settings below.

NOTE: The configuration below may be suitable for a personal domain, where the owner can decide what happens with all messages. For domains that receive messages for other people, a less radical approach may be better, as described in the sections that follow.

1 /etc/postfix/main.cf:
2     # Don't enforce REQUIRETLS when delivering mail with SMTP or LMTP.
3     smtp_requiretls_policy = opportunistic
4     lmtp_requiretls_policy = opportunistic
5     
6     # Don't detect or add a "Require-TLS-ESMTP: yes" header.
7     requiretls_esmtp_header = no

Lines 3-4: These relax REQUIRETLS enforcement when delivering a email to a message store, content filter, or other destination that may not support REQUIRETLS. If a server does not support STARTTLS or REQUIRETLS, then Postfix will simply deliver the message as if the sender did not request REQUIRETLS.
Line 7: The requiretls_esmtp_header feature enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter based on SMTPD_PROXY_README or FILTER_README. This feature can safely be disabled if the domain does not need to enforce REQUIRETLS while delivering or forwarding messages.

LMTP and SMTP-based message stores and content filters

REQUIRETLS is historically not supported by message stores such as Dovecot, and by content filters based on FILTER_README or SMTPD_PROXY_README. The settings below allow for that reality, while also preparing for future REQUIRETLS support.

The Postfix SMTP (LMTP) client supports a permissive REQUIRETLS policy that is suitable for communication with internal message stores and content filters based on FILTER_README or SMTPD_PROXY_README.

opportunistic: STARTTLS and REQUIRETLS support are optional. When the sender requests REQUIRETLS, and an SMTP or LMTP server supports STARTTLS and REQUIRETLS, then send REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.

For a more complete definition of this enforcement level, see the smtp_requiretls_policy parameter documentation.

For REQUIRETLS, the relevant Postfix 3.11 configuration default settings are:

 1 /etc/postfix/main.cf:
 2     smtp_tls_security_level = may
 3     requiretls_esmtp_header = yes
 4     lmtp_requiretls_policy = opportunistic
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13       ...to be completed in section "Communication with external servers"...

Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.

Non-SMTP and non-LMTP content filters

Postfix FILTER_README describes content inspection based on a pipe-to-command approach. For REQUIRETLS, the relevant Postfix 3.11 default setting is:

/etc/postfix/main.cf:
    requiretls_esmtp_header = yes

The requiretls_esmtp_header feature enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.

Communication with external servers

For communication with external servers, the Postfix SMTP client supports multiple enforcement levels:

enforce: When the sender requests REQUIRETLS, require secure lookup of MX hosts (for example, using DNSSEC or HTTPS), require a server certificate match (for example, based on a published DANE or STS policy), and require that the remote server supports REQUIRETLS. Otherwise return the message as undeliverable.

NOTE: this is also used implicitly when no REQUIRETLS policy match is found.
opportunistic+starttls: When the sender requests REQUIRETLS, require that the server supports STARTTLS. Send REQUIRETLS if the server supports REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.
opportunistic: STARTTLS and REQUIRETLS support are optional. When the sender requests REQUIRETLS, and an SMTP or LMTP server supports STARTTLS and REQUIRETLS, then send REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.

For a more complete definition of these enforcement levels, see the smtp_requiretls_policy parameter documentation.

For sending mail with REQUIRETLS, the relevant Postfix 3.11 default settings are shown below, with one suggested setting in a comment (line 2).

The default settings below complete the earlier configuration for message stores and content filters, with an 'enforce' policy for external deliveries (line 13). You can disable the requiretls_esmtp_header feature (line 4) if a configuration does not use content inspection based on SMTPD_PROXY_README or FILTER_README.

 1 /etc/postfix/main.cf:
 2     # smtp_tls_policy_maps = ...dane/sts plugin...
 3     smtp_tls_security_level = may
 4     requiretls_esmtp_header = yes
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13         enforce

New at line 13: The 'enforce' policy for external destinations is technically correct, but is likely to suffer from delivery failures because many domains do not publish a DANE or STS policy, and many MTAs support STARTTLS but not REQUIRETLS. A perhaps more practical policy may be found in the section Relaxing REQUIRETLS for external deliveries.
(Same as before) Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
(Same as before) Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
(Same as before) Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
(Same as before) Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.)

Relaxing REQUIRETLS for external deliveries

It may be desirable to make REQUIRETLS work with today's infrastructure, by keeping the requirement for TLS, but relaxing the requirements that a remote server supports REQUIRETLS and that its server certificate matches a DANE or STS policy. The configuration below makes that change by replacing the default 'enforce' with 'opportunistic+starttls' (line 13).

 1 /etc/postfix/main.cf:
 2     smtp_tls_security_level = may
 3     # smtp_tls_policy_maps = ...dane/sts plugin...
 4     requiretls_esmtp_header = yes
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13         opportunistic+starttls

New at line 13: the 'opportunistic+starttls' policy relaxes the requirement that every MTA in the forward path of a message supports REQUIRETLS, but in practice only one network hop needs to be secured: from a sender's perimeter MTA to a receiver's perimeter MTA. The network connections between user agents and their respective perimeters are assumed to be already secure.
(Same as before) Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
(Same as before) Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
(Same as before) Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
(Same as before) Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.)

An experiment: testing REQUIRETLS support

The 'opportunistic' enforcement level may be useful to discover REQUIRETLS support globally. The idea is to turn on REQUIRETLS for all outbound mail, and watch in Postfix TLS status logging how often delivery is logged as "requiretls" (all requirements satisfied), "requiretls:nocertmatch" (no DANE or STS policy, or certificate not trusted or not matched), "requiretls:none" (no REQUIRETLS support), or "requiretls:nostarttls". For more details on this logging format, see smtp_log_tls_feature_status.

Requesting REQUIRETLS without SMTP

There are two options:

Specify the Postfix-specific "sendmail -Orequiretls=yes" command-line option. This option is always available, but may not be convenient to use.
Add a Postfix-specific "Require-TLS-ESMTP: yes" message header. This is easier to use, but requires the setting "requiretls_esmtp_header = yes" which is not recommended for systems without content filters based on SMTPD_PROXY_README or FILTER_README.

Question: perhaps there needs to be a parameter setting to request REQUIRETLS for specific email sources or contexts?

Non-delivery notifications

By default, Postfix redacts an undeliverable REQUIRETLS message as described in RFC 8689, before returning it to the sender:

Remove the label "this message needs REQUIRETLS". The purpose is to avoid loss of notifications when a reverse path does not support REQUIRETLS, even though the forward path supported it.
Return only the message header, as if the message was received with the RFC 3461 DSN option "RET=HDRS". The purpose is to limit the amount of information that may be exposed in plaintext.

The relevant default setting is:

/etc/postfix/main.cf:
    requiretls_redact_dsn = yes

When a message was received with a "TLS-Required: no" header, and REQUIRETLS was not requested, the "TLS-Required: no" header is copied to the delivery status notification.

REQUIRETLS quick summary

The REQUIRETLS extension in ESMTP allows a sender to request that a message will be sent over connections that are protected with TLS. RFC 8689 defines two SMTP features:

A message header "TLS-Required: no" that disables TLS enforcement: do not require a server certificate match, and allow falling back to plaintext if TLS is unavailable. This may be useful to report a TLS problem, as described in TLSRPT_README. This feature has lower precedence than REQUIRETLS, and is not discussed further in this document.
An ESMTP protocol extension named "REQUIRETLS" that an SMTP server may list in its EHLO response, and that an SMTP client may request in a MAIL FROM command. This extension can be used only in an encrypted session, as illustrated with the fragment below, where C=client and S=server.
```
. . .
C: STARTTLS
S: 220 Ready to start TLS
C: EHLO client.example.org
S: 250-mail.example.com 
   . . .
   250 REQUIRETLS
C: MAIL FROM:<sender@@example.org> REQUIRETLS
S: 250 OK
. . .
```
RFC 8689 applies equally to message relay [RFC 5321], submission [RFC 6409], and the LMTP Local Mail Transfer Protocol [RFC 2033].
REQUIRETLS is an end-to-end feature, unlike SMTP which is hop-by-hop. When a sender requests REQUIRETLS, each server in the forward path must support REQUIRETLS.
Each connection in the forward path must be made to a server that has been looked up securely (for example, with DNSSEC or HTTPS).
Each server certificate must be verified. To match a server certificate, the Postfix SMTP client needs to use an appropriate policy type:
- A TLS policy type 'secure' or 'verify', with certificate name matching info. For example, a policy returned by an MTA-STS plugin that looks up certificate matching info using HTTPS;
- A TLS policy type 'dane-only', which looks up certificate or public-key matching info using DNSSEC. For example, a policy that is returned by a DANE+STS plugin;
- A TLS policy type 'dane', provided that both the nexthop domain and its MX hosts are in DNSSEC-signed zones, and usable DNSSEC-signed TLSA records are discovered. In other words, the effective TLS policy remains DANE and is not downgraded because the destination lacks DNSSEC and/or usable TLSA records;
- A TLS policy type 'fingerprint', with digital fingerprints. This is a non-scalable solution for special deployments, mentioned here only for completeness.
A message that requires REQUIRETLS must be returned to the sender if any of the above requirements is not satisfied (no STARTTLS support, no secure lookup of MX servers, no trusted or no matching server certificate, or no server that announces REQUIRETLS support).
Returning an undeliverable message that requires REQUIRETLS comes with its own challenges: the return path may differ from the forward path, and the return path may not support REQUIRETLS all the way back to the sender, even if the forward path supported REQUIRETLS. By default, Postfix follows RFC 8689 and redacts bounce messages so that they can be sent without REQUIRETLS.

Credits

In Postfix 3.10, Wietse Venema refactored SMTPUTF8 support and extended it to propagate REQUIRETLS and "TLS-Required: no" information.
In Postfix 3.11, Wietse added REQUIRETLS support to the Postfix SMTP client; added a "tls=status/requiretls=status" field to the Postfix delivery status logging; added smtp_requiretls_policy support; added support for the "Require-TLS-ESMTP: yes" header to propagate REQUIRETLS through non-Postfix programs, specifically content filters.

@ 1.1.1.1 log @Import postfix 3.11.2 (previous was 3.10.1) Changes in 3.11.2 Bugfix (defect introduced: Postfix 3.11): the proxymap(8) daemon dereferenced an uninitialized pointer after a request protocol error. This daemon is not exposed to local or remote users. Found by Claude Opus 4.6. Bugfix (defect introduced: 20260309) a change, to set the service_name default value to "amnesiac", violated a test that parameter names in postconf output must match 1:1 with parameter names in the postlink script. Changes in 3.11.1 Bugfix (defect introduced: 20260219): alias_maps errors when default_database_type was not set in main.cf. Fix by Michael Tokarev. Bugfix (defect introduced: Postfix 3.0): buffer over-read when Postfix is configured with an enhanced status code not followed by other text. For example, "5.7.2" without text after the three-number code, in an access(5) table, header or body checks, or with "$rbl_code $rbl_text" in rbl_reply_maps or default_rbl_reply. These are all uncommon configurations. Problem reported by Kamil Frankowicz. Bugfix (defect introduced: Postfix 3.3): null pointer in nbdb_reindexd(8) because the "service_name" value was not propagated. Report by Michael Tokarev. During Postfix start-up, avoid a spurious error message from nbdb_reindexd(8), when non_bdb_migration_level disables automatic re-indexing. Changes in 3.11.0 Postfix stable release 3.11.0 is available. Postfix 3.7 - 3.10 were updated a few weeks ago; after that, Postfix 3.7 will no longer be updated. The main changes are below. See the RELEASE_NOTES file for further details. Berkeley DB migration: Some (Linux) distributions are removing support for BerkeleyDB databases (In Postfix, this means we lose support for the hash: and btree: lookup tables). See NON_BERKELEYDB_README for manual and partially automatic migration from btree: to lmdb:, and from hash: to lmdb: or cdb:. The loss of BerkeleyDB affects Mailman versions that want to execute commands like "postmap hash:/path/to/file" when a mailing list is added or removed. Postfix provides a way to redirect such commands to a supported database type. You don't have to wait until BerkeleyDB support is removed. It can make sense to migrate while BerkeleyDB support is still available (mainly, less downtime). Changes in TLS support: Default TLS security. The Postfix SMTP client smtp_tls_security_level default value is "may" if Postfix was built with TLS support, and the compatibility_level is 3.11 or higher. Support for the RFC 8689 "REQUIRETLS" verb in ESMTP. This requires that every SMTP (and LMTP) server in the forward path is strongly authenticated with DANE, STS, or equivalent, and that every server announces REQUIRETLS support. See REQUIRETLS_README for suggestions to carefully enforce REQUIRETLS without causing massive mail delivery problems. Logging the TLS security level. This shows the desired and actual TLS security level enforcement status and, if a message requests REQUIRETLS, the REQUIRETLS policy enforcement status. For a list of examples see smtp_log_tls_feature_status Workaround for an interface mismatch between the Postfix SMTP client and MTA-STS policy plugins. This introduces a new parameter smtp_tls_enforce_sts_mx_patterns (default: "yes"). The MTA-STS plugin configuration needs to enable TLSRPT support, so that it forwards STS policy attributes to Postfix. Both postfix-tlspol and postfix-mta-sts-resolver have been updated accordingly. With this, the Postfix SMTP client will connect to an MX host only if its name matches any STS policy MX host pattern, and will match a server certificate against the MX hostname. Otherwise, the old behavior stays in effect: connect to any MX host listed in DNS, and match a server certificate against any STS policy MX host pattern. Post-quantum cryptography support. With OpenSSL 3.5 and later, change the tls_eecdh_auto_curves default value to avoid problems with network infrastructure that mishandles TLS hello messages larger than one (Ethernet) TCP segment. This problem is more generally known as "protocol ossification". Miscellaneous changes: Deprecation of obsolete parameters. Postfix programs log a warning that these parameters will be removed. See DEPRECATION_README for a list of deprecated parameters. JSON output support with "postconf -j|-jM|-jF|-jP", "postalias -jq|-js", "postmap -jq|-js", and "postmulti -jl". No support is planned for JSON input support. Milter support: improved Milter error handling for messages that arrive over a long-lived SMTP connection, by changing the default milter_default_action from "tempfail" to the new "shutdown" action (i.e. disconnect the remote SMTP client). This was already back-ported to earlier stable releases. For more changes in the 3.10 branch see: https://www.postfix.org/announcements.html @ text @@ 1.1.1.1.2.1 log @file REQUIRETLS_README.html was added on branch netbsd-11 on 2026-05-11 17:13:37 +0000 @ text @d1 572 @ 1.1.1.1.2.2 log @Pull up the following, requested by christos in ticket #283: external/ibm-public/postfix//dist/README_FILES/NON_BERKELEYDB_README up to external/ibm-public/postfix//dist/README_FILES/REQUIRETLS_README up to external/ibm-public/postfix//dist/conf/postfix-non-bdb-script up to external/ibm-public/postfix//dist/html/NON_BERKELEYDB_README.html up to external/ibm-public/postfix//dist/html/REQUIRETLS_README.html up to external/ibm-public/postfix//dist/html/nbdb_reindexd.8.html up to external/ibm-public/postfix//dist/html/postfix-non-bdb.1.html up to external/ibm-public/postfix//dist/man/man1/postfix-non-bdb.1 up to external/ibm-public/postfix//dist/man/man8/nbdb_reindexd.8 up to external/ibm-public/postfix//dist/mantools/check-proxy-type-table up to external/ibm-public/postfix//dist/proto/NON_BERKELEYDB_README.html up to external/ibm-public/postfix//dist/proto/REQUIRETLS_README.html up to external/ibm-public/postfix//dist/src/cleanup/cleanup_message_test.c up to external/ibm-public/postfix//dist/src/global/ehlo_mask_test.c up to external/ibm-public/postfix//dist/src/global/nbdb_clnt.c up to external/ibm-public/postfix//dist/src/global/allowed_prefix.c up to external/ibm-public/postfix//dist/src/global/allowed_prefix.h up to external/ibm-public/postfix//dist/src/global/allowed_prefix_test.c up to external/ibm-public/postfix//dist/src/global/dict_sqlite_test.c up to external/ibm-public/postfix//dist/src/global/haproxy_srvr_test.c up to external/ibm-public/postfix//dist/src/global/login_sender_match_test.c up to external/ibm-public/postfix//dist/src/global/nbdb_clnt.h up to external/ibm-public/postfix//dist/src/global/nbdb_redirect.c up to external/ibm-public/postfix//dist/src/global/nbdb_redirect.h up to external/ibm-public/postfix//dist/src/global/nbdb_redirect_test.c up to external/ibm-public/postfix//dist/src/global/nbdb_surrogate.c up to external/ibm-public/postfix//dist/src/global/nbdb_surrogate.h up to external/ibm-public/postfix//dist/src/global/nbdb_surrogate_test.c up to external/ibm-public/postfix//dist/src/global/nbdb_util.c up to external/ibm-public/postfix//dist/src/global/nbdb_util.h up to external/ibm-public/postfix//dist/src/global/nbdb_util_test.c up to external/ibm-public/postfix//dist/src/global/pol_stats.c up to external/ibm-public/postfix//dist/src/global/pol_stats.h up to external/ibm-public/postfix//dist/src/global/pol_stats_test.c up to external/ibm-public/postfix//dist/src/postalias/mode_conflict_test.in up to external/ibm-public/postfix//dist/src/postalias/mode_conflict_test.ref up to external/ibm-public/postfix//dist/src/postconf/test77-main.cf up to external/ibm-public/postfix//dist/src/postconf/test77.ref up to external/ibm-public/postfix//dist/src/postconf/test78.ref up to external/ibm-public/postfix//dist/src/postconf/test79.ref up to external/ibm-public/postfix//dist/src/postconf/test80.ref up to external/ibm-public/postfix//dist/src/postconf/test81.ref up to external/ibm-public/postfix//dist/src/postconf/test82.ref up to external/ibm-public/postfix//dist/src/postconf/test83.ref up to external/ibm-public/postfix//dist/src/postconf/test84.ref up to external/ibm-public/postfix//dist/src/postconf/test85.ref up to external/ibm-public/postfix//dist/src/postconf/test86.ref up to external/ibm-public/postfix//dist/src/postconf/test87.ref up to external/ibm-public/postfix//dist/src/postconf/test91.ref up to external/ibm-public/postfix//dist/src/postmap/mode_conflict_test.in up to external/ibm-public/postfix//dist/src/postmap/mode_conflict_test.ref up to external/ibm-public/postfix//dist/src/postmulti/fake_strcmp.c up to external/ibm-public/postfix//dist/src/smtp/smtp_reqtls_policy.c up to external/ibm-public/postfix//dist/src/smtp/smtp_reqtls_policy.h up to external/ibm-public/postfix//dist/src/smtp/smtp_reqtls_policy_test.c up to external/ibm-public/postfix//dist/src/smtp/smtp_tls_policy_test.c up to external/ibm-public/postfix//dist/src/smtpd/smtpd_peer_test.c up to external/ibm-public/postfix//dist/src/util/dict_union_test.c up to external/ibm-public/postfix//dist/src/util/hash_fnv_test.c up to external/ibm-public/postfix//dist/src/util/mac_midna.h up to external/ibm-public/postfix//dist/src/util/normalize_v4mapped_addr.c up to external/ibm-public/postfix//dist/src/util/dict_debug.h up to external/ibm-public/postfix//dist/src/util/dict_debug_test.ref up to external/ibm-public/postfix//dist/src/util/dict_debug_test.sh up to external/ibm-public/postfix//dist/src/util/dict_pipe_test.c up to external/ibm-public/postfix//dist/src/util/mac_midna.c up to external/ibm-public/postfix//dist/src/util/normalize_v4mapped_addr.h up to external/ibm-public/postfix//dist/src/util/normalize_v4mapped_addr_test.c up to external/ibm-public/postfix//dist/src/util/ossl_digest.c up to external/ibm-public/postfix//dist/src/util/ossl_digest.h up to external/ibm-public/postfix//dist/src/util/ossl_digest_test.c up to external/ibm-public/postfix//dist/src/util/wrap_stat.c up to external/ibm-public/postfix//dist/src/util/wrap_stat.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/Makefile.in up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_index_as.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_index_as.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_index_as_test.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_process.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_process.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_process_test.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_reindexd.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_reindexd.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_safe.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_safe.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_safe_test.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_sniffer.c up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_sniffer.h up to external/ibm-public/postfix//dist/src/nbdb_reindexd/nbdb_sniffer_test.c up to external/ibm-public/postfix//dist/src/testing/Makefile.in up to external/ibm-public/postfix//dist/src/testing/dict_test_helper.c up to external/ibm-public/postfix//dist/src/testing/dict_test_helper.h up to external/ibm-public/postfix//dist/src/testing/mock_dict.c up to external/ibm-public/postfix//dist/src/testing/mock_dict.h up to external/ibm-public/postfix//dist/src/testing/mock_open_as.c up to external/ibm-public/postfix//dist/src/testing/mock_open_as.h up to 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external/ibm-public/postfix/Makefile.inc up to 1.32 external/ibm-public/postfix/dist/HISTORY up to 1.1.1.31 external/ibm-public/postfix/dist/INSTALL up to 1.1.1.11 external/ibm-public/postfix/dist/Makefile.in up to 1.1.1.12 external/ibm-public/postfix/dist/RELEASE_NOTES up to 1.1.1.19 external/ibm-public/postfix/dist/makedefs up to 1.18 external/ibm-public/postfix/dist/README_FILES/AAAREADME up to 1.1.1.8 external/ibm-public/postfix/dist/README_FILES/CDB_README up to 1.1.1.4 external/ibm-public/postfix/dist/README_FILES/COMPATIBILITY_README up to 1.1.1.5 external/ibm-public/postfix/dist/README_FILES/DATABASE_README up to 1.1.1.11 external/ibm-public/postfix/dist/README_FILES/DEPRECATION_README up to 1.1.1.2 external/ibm-public/postfix/dist/README_FILES/INSTALL up to 1.12 external/ibm-public/postfix/dist/README_FILES/MULTI_INSTANCE_README up to 1.1.1.8 external/ibm-public/postfix/dist/README_FILES/MYSQL_README up to 1.1.1.7 external/ibm-public/postfix/dist/README_FILES/OVERVIEW up to 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external/ibm-public/postfix/dist/conf/postfix-files up to 1.11 external/ibm-public/postfix/dist/conf/postfix-script up to 1.6 external/ibm-public/postfix/dist/conf/postfix-tls-script up to 1.6 external/ibm-public/postfix/dist/conf/relocated up to 1.1.1.5 external/ibm-public/postfix/dist/conf/transport up to 1.1.1.6 external/ibm-public/postfix/dist/conf/virtual up to 1.1.1.8 external/ibm-public/postfix/dist/html/CDB_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/html/COMPATIBILITY_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/html/DATABASE_README.html up to 1.1.1.12 external/ibm-public/postfix/dist/html/DEPRECATION_README.html up to 1.1.1.2 external/ibm-public/postfix/dist/html/INSTALL.html up to 1.12 external/ibm-public/postfix/dist/html/MULTI_INSTANCE_README.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/MYSQL_README.html up to 1.1.1.7 external/ibm-public/postfix/dist/html/Makefile.in up to 1.1.1.9 external/ibm-public/postfix/dist/html/OVERVIEW.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/SASL_README.html up to 1.1.1.13 external/ibm-public/postfix/dist/html/SMTPUTF8_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/html/SOHO_README.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/STANDARD_CONFIGURATION_README.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/TLSRPT_README.html up to 1.1.1.2 external/ibm-public/postfix/dist/html/UUCP_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/html/VIRTUAL_README.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/XCLIENT_README.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/access.5.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/aliases.5.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/bounce.8.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/canonical.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/cidr_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/cleanup.8.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/defer.8.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/discard.8.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/error.8.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/generic.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/index.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/ldap_table.5.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/lmdb_table.5.html up to 1.1.1.6 external/ibm-public/postfix/dist/html/lmtp.8.html up to 1.1.1.14 external/ibm-public/postfix/dist/html/mailq.1.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/makedefs.1.html up to 1.1.1.5 external/ibm-public/postfix/dist/html/memcache_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/mongodb_table.5.html up to 1.1.1.2 external/ibm-public/postfix/dist/html/mysql_table.5.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/newaliases.1.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/nisplus_table.5.html up to 1.1.1.7 external/ibm-public/postfix/dist/html/oqmgr.8.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/pcre_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/pgsql_table.5.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/postalias.1.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/postconf.1.html up to 1.1.1.13 external/ibm-public/postfix/dist/html/postconf.5.html up to 1.22 external/ibm-public/postfix/dist/html/postdrop.1.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/postfix-manuals.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/postfix-tls.1.html up to 1.1.1.5 external/ibm-public/postfix/dist/html/postfix.1.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/postlog.1.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/postmap.1.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/postmulti.1.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/postqueue.1.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/postscreen.8.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/posttls-finger.1.html up to 1.1.1.7 external/ibm-public/postfix/dist/html/proxymap.8.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/qmgr.8.html up to 1.1.1.11 external/ibm-public/postfix/dist/html/regexp_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/relocated.5.html up to 1.1.1.7 external/ibm-public/postfix/dist/html/sendmail.1.html up to 1.1.1.10 external/ibm-public/postfix/dist/html/smtp.8.html up to 1.1.1.14 external/ibm-public/postfix/dist/html/smtpd.8.html up to 1.1.1.15 external/ibm-public/postfix/dist/html/socketmap_table.5.html up to 1.1.1.7 external/ibm-public/postfix/dist/html/sqlite_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/tcp_table.5.html up to 1.1.1.8 external/ibm-public/postfix/dist/html/trace.8.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/transport.5.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/virtual.5.html up to 1.1.1.9 external/ibm-public/postfix/dist/html/virtual.8.html up to 1.1.1.9 external/ibm-public/postfix/dist/man/Makefile.in up to 1.1.1.9 external/ibm-public/postfix/dist/man/man1/makedefs.1 up to 1.5 external/ibm-public/postfix/dist/man/man1/postalias.1 up to 1.5 external/ibm-public/postfix/dist/man/man1/postconf.1 up to 1.6 external/ibm-public/postfix/dist/man/man1/postdrop.1 up to 1.6 external/ibm-public/postfix/dist/man/man1/postfix-tls.1 up to 1.4 external/ibm-public/postfix/dist/man/man1/postfix.1 up to 1.8 external/ibm-public/postfix/dist/man/man1/postlog.1 up to 1.7 external/ibm-public/postfix/dist/man/man1/postmap.1 up to 1.5 external/ibm-public/postfix/dist/man/man1/postmulti.1 up to 1.5 external/ibm-public/postfix/dist/man/man1/postqueue.1 up to 1.6 external/ibm-public/postfix/dist/man/man1/posttls-finger.1 up to 1.7 external/ibm-public/postfix/dist/man/man1/sendmail.1 up to 1.6 external/ibm-public/postfix/dist/man/man5/access.5 up to 1.6 external/ibm-public/postfix/dist/man/man5/aliases.5 up to 1.7 external/ibm-public/postfix/dist/man/man5/canonical.5 up to 1.6 external/ibm-public/postfix/dist/man/man5/cidr_table.5 up to 1.7 external/ibm-public/postfix/dist/man/man5/generic.5 up to 1.6 external/ibm-public/postfix/dist/man/man5/ldap_table.5 up to 1.7 external/ibm-public/postfix/dist/man/man5/lmdb_table.5 up to 1.4 external/ibm-public/postfix/dist/man/man5/memcache_table.5 up to 1.3 external/ibm-public/postfix/dist/man/man5/mongodb_table.5 up to 1.3 external/ibm-public/postfix/dist/man/man5/mysql_table.5 up to 1.7 external/ibm-public/postfix/dist/man/man5/nisplus_table.5 up to 1.3 external/ibm-public/postfix/dist/man/man5/pcre_table.5 up to 1.6 external/ibm-public/postfix/dist/man/man5/pgsql_table.5 up to 1.7 external/ibm-public/postfix/dist/man/man5/postconf.5 up to 1.21 external/ibm-public/postfix/dist/man/man5/regexp_table.5 up to 1.6 external/ibm-public/postfix/dist/man/man5/relocated.5 up to 1.5 external/ibm-public/postfix/dist/man/man5/socketmap_table.5 up to 1.5 external/ibm-public/postfix/dist/man/man5/sqlite_table.5 up to 1.5 external/ibm-public/postfix/dist/man/man5/tcp_table.5 up to 1.4 external/ibm-public/postfix/dist/man/man5/transport.5 up to 1.5 external/ibm-public/postfix/dist/man/man5/virtual.5 up to 1.7 external/ibm-public/postfix/dist/man/man8/bounce.8 up to 1.6 external/ibm-public/postfix/dist/man/man8/cleanup.8 up to 1.6 external/ibm-public/postfix/dist/man/man8/discard.8 up to 1.4 external/ibm-public/postfix/dist/man/man8/error.8 up to 1.4 external/ibm-public/postfix/dist/man/man8/oqmgr.8 up to 1.4 external/ibm-public/postfix/dist/man/man8/postscreen.8 up to 1.7 external/ibm-public/postfix/dist/man/man8/proxymap.8 up to 1.5 external/ibm-public/postfix/dist/man/man8/qmgr.8 up to 1.5 external/ibm-public/postfix/dist/man/man8/smtp.8 up to 1.7 external/ibm-public/postfix/dist/man/man8/smtpd.8 up to 1.7 external/ibm-public/postfix/dist/man/man8/virtual.8 up to 1.5 external/ibm-public/postfix/dist/mantools/check-postconf-unimplemented up to 1.1.1.2 external/ibm-public/postfix/dist/mantools/check-spell-history up to 1.1.1.2 external/ibm-public/postfix/dist/mantools/check-spell-proto-html up to 1.1.1.3 external/ibm-public/postfix/dist/mantools/dehtml up to 1.1.1.3 external/ibm-public/postfix/dist/mantools/postconf2man up to 1.1.1.7 external/ibm-public/postfix/dist/mantools/postlink up to 1.1.1.15 external/ibm-public/postfix/dist/mantools/srctoman up to 1.1.1.5 external/ibm-public/postfix/dist/proto/CDB_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/proto/COMPATIBILITY_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/proto/DATABASE_README.html up to 1.1.1.12 external/ibm-public/postfix/dist/proto/DEPRECATION_README.html up to 1.1.1.2 external/ibm-public/postfix/dist/proto/INSTALL.html up to 1.12 external/ibm-public/postfix/dist/proto/MULTI_INSTANCE_README.html up to 1.1.1.10 external/ibm-public/postfix/dist/proto/MYSQL_README.html up to 1.1.1.7 external/ibm-public/postfix/dist/proto/Makefile.in up to 1.1.1.9 external/ibm-public/postfix/dist/proto/OVERVIEW.html up to 1.1.1.8 external/ibm-public/postfix/dist/proto/SASL_README.html up to 1.1.1.13 external/ibm-public/postfix/dist/proto/SMTPUTF8_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/proto/STANDARD_CONFIGURATION_README.html up to 1.1.1.8 external/ibm-public/postfix/dist/proto/TLSRPT_README.html up to 1.1.1.2 external/ibm-public/postfix/dist/proto/UUCP_README.html up to 1.1.1.5 external/ibm-public/postfix/dist/proto/VIRTUAL_README.html up to 1.1.1.6 external/ibm-public/postfix/dist/proto/XCLIENT_README.html up to 1.1.1.8 external/ibm-public/postfix/dist/proto/access up to 1.1.1.10 external/ibm-public/postfix/dist/proto/aliases up to 1.1.1.8 external/ibm-public/postfix/dist/proto/canonical up to 1.1.1.7 external/ibm-public/postfix/dist/proto/cidr_table up to 1.1.1.8 external/ibm-public/postfix/dist/proto/generic up to 1.1.1.6 external/ibm-public/postfix/dist/proto/index.html up to 1.1.1.2 external/ibm-public/postfix/dist/proto/ldap_table up to 1.1.1.9 external/ibm-public/postfix/dist/proto/lmdb_table up to 1.1.1.4 external/ibm-public/postfix/dist/proto/memcache_table up to 1.1.1.5 external/ibm-public/postfix/dist/proto/mongodb_table up to 1.1.1.2 external/ibm-public/postfix/dist/proto/mysql_table up to 1.1.1.10 external/ibm-public/postfix/dist/proto/nisplus_table up to 1.1.1.4 external/ibm-public/postfix/dist/proto/pcre_table up to 1.1.1.8 external/ibm-public/postfix/dist/proto/pgsql_table up to 1.1.1.10 external/ibm-public/postfix/dist/proto/postconf.html.prolog up to 1.1.1.7 external/ibm-public/postfix/dist/proto/postconf.man.prolog up to 1.1.1.5 external/ibm-public/postfix/dist/proto/postconf.proto up to 1.21 external/ibm-public/postfix/dist/proto/regexp_table up to 1.1.1.8 external/ibm-public/postfix/dist/proto/relocated up to 1.1.1.5 external/ibm-public/postfix/dist/proto/socketmap_table up to 1.1.1.5 external/ibm-public/postfix/dist/proto/sqlite_table up to 1.1.1.6 external/ibm-public/postfix/dist/proto/stop up to 1.1.1.9 external/ibm-public/postfix/dist/proto/stop.double-cc up to 1.1.1.4 external/ibm-public/postfix/dist/proto/stop.double-history up to 1.1.1.3 external/ibm-public/postfix/dist/proto/stop.double-install-proto-text up to 1.1.1.3 external/ibm-public/postfix/dist/proto/stop.double-proto-html up to 1.1.1.4 external/ibm-public/postfix/dist/proto/stop.spell-cc up to 1.1.1.4 external/ibm-public/postfix/dist/proto/stop.spell-history up to 1.1.1.3 external/ibm-public/postfix/dist/proto/stop.spell-proto-html up to 1.1.1.4 external/ibm-public/postfix/dist/proto/tcp_table up to 1.1.1.5 external/ibm-public/postfix/dist/proto/transport up to 1.1.1.6 external/ibm-public/postfix/dist/proto/virtual up to 1.1.1.8 external/ibm-public/postfix/dist/src/bounce/Makefile.in up to 1.1.1.7 external/ibm-public/postfix/dist/src/bounce/bounce.c up to 1.6 external/ibm-public/postfix/dist/src/bounce/bounce_notify_service.c up to 1.4 external/ibm-public/postfix/dist/src/bounce/bounce_notify_util.c up to 1.6 external/ibm-public/postfix/dist/src/bounce/bounce_notify_verp.c up to 1.4 external/ibm-public/postfix/dist/src/bounce/bounce_one_service.c up to 1.4 external/ibm-public/postfix/dist/src/bounce/bounce_trace_service.c up to 1.4 external/ibm-public/postfix/dist/src/bounce/bounce_warn_service.c up to 1.4 external/ibm-public/postfix/dist/src/cleanup/Makefile.in up to 1.1.1.11 external/ibm-public/postfix/dist/src/cleanup/cleanup.c up to 1.10 external/ibm-public/postfix/dist/src/cleanup/cleanup.h up to 1.12 external/ibm-public/postfix/dist/src/cleanup/cleanup_api.c up to 1.6 external/ibm-public/postfix/dist/src/cleanup/cleanup_bounce.c up to 1.4 external/ibm-public/postfix/dist/src/cleanup/cleanup_init.c up to 1.9 external/ibm-public/postfix/dist/src/cleanup/cleanup_message.c up to 1.6 external/ibm-public/postfix/dist/src/cleanup/cleanup_milter.c up to 1.7 external/ibm-public/postfix/dist/src/cleanup/cleanup_out_recipient.c up to 1.6 external/ibm-public/postfix/dist/src/cleanup/cleanup_state.c up to 1.6 external/ibm-public/postfix/dist/src/discard/Makefile.in up to 1.1.1.5 external/ibm-public/postfix/dist/src/discard/discard.c up to 1.4 external/ibm-public/postfix/dist/src/dns/dns.h up to 1.8 external/ibm-public/postfix/dist/src/dns/dns_lookup.c up to 1.10 external/ibm-public/postfix/dist/src/error/Makefile.in up to 1.1.1.5 external/ibm-public/postfix/dist/src/error/error.c up to 1.4 external/ibm-public/postfix/dist/src/global/Makefile.in up to 1.1.1.12 external/ibm-public/postfix/dist/src/global/abounce.c up to 1.5 external/ibm-public/postfix/dist/src/global/ascii_header_text.c up to 1.3 external/ibm-public/postfix/dist/src/global/ascii_header_text.h up to 1.3 external/ibm-public/postfix/dist/src/global/bounce.c up to 1.5 external/ibm-public/postfix/dist/src/global/bounce.h up to 1.3 external/ibm-public/postfix/dist/src/global/cleanup_strflags.c up to 1.3 external/ibm-public/postfix/dist/src/global/cleanup_user.h up to 1.5 external/ibm-public/postfix/dist/src/global/config_known_tcp_ports.c up to 1.3 external/ibm-public/postfix/dist/src/global/data_redirect.c up to 1.3 external/ibm-public/postfix/dist/src/global/defer.c up to 1.5 external/ibm-public/postfix/dist/src/global/defer.h up to 1.3 external/ibm-public/postfix/dist/src/global/deliver_pass.c up to 1.5 external/ibm-public/postfix/dist/src/global/dict_ldap.c up to 1.7 external/ibm-public/postfix/dist/src/global/dict_memcache.c up to 1.4 external/ibm-public/postfix/dist/src/global/dict_mongodb.c up to 1.3 external/ibm-public/postfix/dist/src/global/dict_mysql.c up to 1.6 external/ibm-public/postfix/dist/src/global/dict_pgsql.c up to 1.6 external/ibm-public/postfix/dist/src/global/dict_proxy.c up to 1.4 external/ibm-public/postfix/dist/src/global/dict_sqlite.c up to 1.6 external/ibm-public/postfix/dist/src/global/dict_sqlite.h up to 1.2 external/ibm-public/postfix/dist/src/global/dsn_util.c up to 1.2 external/ibm-public/postfix/dist/src/global/ehlo_mask.c up to 1.4 external/ibm-public/postfix/dist/src/global/ehlo_mask.h up to 1.4 external/ibm-public/postfix/dist/src/global/haproxy_srvr.c up to 1.5 external/ibm-public/postfix/dist/src/global/haproxy_srvr.h up to 1.3 external/ibm-public/postfix/dist/src/global/header_opts.c up to 1.4 external/ibm-public/postfix/dist/src/global/header_opts.h up to 1.4 external/ibm-public/postfix/dist/src/global/log_adhoc.c up to 1.4 external/ibm-public/postfix/dist/src/global/log_adhoc.h up to 1.2 external/ibm-public/postfix/dist/src/global/login_sender_match.c up to 1.3 external/ibm-public/postfix/dist/src/global/mail_conf.c up to 1.5 external/ibm-public/postfix/dist/src/global/mail_conf.h up to 1.4 external/ibm-public/postfix/dist/src/global/mail_params.c up to 1.7 external/ibm-public/postfix/dist/src/global/mail_params.h up to 1.21 external/ibm-public/postfix/dist/src/global/mail_proto.h up to 1.7 external/ibm-public/postfix/dist/src/global/mail_version.h up to 1.8 external/ibm-public/postfix/dist/src/global/maps.c up to 1.6 external/ibm-public/postfix/dist/src/global/mime_garb3.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/global/mime_state.c up to 1.4 external/ibm-public/postfix/dist/src/global/mime_state.h up to 1.2 external/ibm-public/postfix/dist/src/global/mynetworks.c up to 1.3 external/ibm-public/postfix/dist/src/global/namadr_list.in up to 1.1.1.5 external/ibm-public/postfix/dist/src/global/namadr_list.ref up to 1.1.1.6 external/ibm-public/postfix/dist/src/global/own_inet_addr.c up to 1.3 external/ibm-public/postfix/dist/src/global/pipe_command.c up to 1.3 external/ibm-public/postfix/dist/src/global/post_mail.c up to 1.6 external/ibm-public/postfix/dist/src/global/rec_type.h up to 1.5 external/ibm-public/postfix/dist/src/global/reject_deliver_request.c up to 1.3 external/ibm-public/postfix/dist/src/global/rfc2047_code.c up to 1.3 external/ibm-public/postfix/dist/src/global/rfc2047_code.h up to 1.3 external/ibm-public/postfix/dist/src/global/sendopts.c up to 1.3 external/ibm-public/postfix/dist/src/global/sent.c up to 1.4 external/ibm-public/postfix/dist/src/global/sent.h up to 1.3 external/ibm-public/postfix/dist/src/global/server_acl.c up to 1.5 external/ibm-public/postfix/dist/src/global/trace.c up to 1.4 external/ibm-public/postfix/dist/src/global/trace.h up to 1.2 external/ibm-public/postfix/dist/src/global/verify.c up to 1.5 external/ibm-public/postfix/dist/src/global/verify.h up to 1.2 external/ibm-public/postfix/dist/src/local/Makefile.in up to 1.1.1.10 external/ibm-public/postfix/dist/src/local/forward.c up to 1.6 external/ibm-public/postfix/dist/src/local/local.c up to 1.6 external/ibm-public/postfix/dist/src/local/local.h up to 1.4 external/ibm-public/postfix/dist/src/master/Makefile.in up to 1.1.1.9 external/ibm-public/postfix/dist/src/master/event_server.c up to 1.5 external/ibm-public/postfix/dist/src/master/multi_server.c up to 1.5 external/ibm-public/postfix/dist/src/milter/milter8.c up to 1.7 external/ibm-public/postfix/dist/src/milter/test-milter.c up to 1.5 external/ibm-public/postfix/dist/src/oqmgr/Makefile.in up to 1.1.1.7 external/ibm-public/postfix/dist/src/oqmgr/qmgr.c up to 1.4 external/ibm-public/postfix/dist/src/oqmgr/qmgr_bounce.c up to 1.2 external/ibm-public/postfix/dist/src/oqmgr/qmgr_defer.c up to 1.2 external/ibm-public/postfix/dist/src/oqmgr/qmgr_message.c up to 1.6 external/ibm-public/postfix/dist/src/pipe/Makefile.in up to 1.1.1.6 external/ibm-public/postfix/dist/src/pipe/pipe.c up to 1.6 external/ibm-public/postfix/dist/src/postalias/Makefile.in up to 1.1.1.8 external/ibm-public/postfix/dist/src/postalias/postalias.c up to 1.7 external/ibm-public/postfix/dist/src/postcat/postcat.c up to 1.6 external/ibm-public/postfix/dist/src/postconf/Makefile.in up to 1.1.1.13 external/ibm-public/postfix/dist/src/postconf/extract.awk up to 1.1.1.7 external/ibm-public/postfix/dist/src/postconf/postconf.c up to 1.6 external/ibm-public/postfix/dist/src/postconf/postconf.h up to 1.6 external/ibm-public/postfix/dist/src/postconf/postconf_builtin.c up to 1.5 external/ibm-public/postfix/dist/src/postconf/postconf_dbms.c up to 1.7 external/ibm-public/postfix/dist/src/postconf/postconf_edit.c up to 1.4 external/ibm-public/postfix/dist/src/postconf/postconf_lookup.c up to 1.5 external/ibm-public/postfix/dist/src/postconf/postconf_main.c up to 1.5 external/ibm-public/postfix/dist/src/postconf/postconf_master.c up to 1.9 external/ibm-public/postfix/dist/src/postconf/postconf_unused.c up to 1.3 external/ibm-public/postfix/dist/src/postconf/postconf_user.c up to 1.6 external/ibm-public/postfix/dist/src/postconf/test18.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/postconf/test2.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/postconf/test28.ref up to 1.1.1.4 external/ibm-public/postfix/dist/src/postconf/test29.ref up to 1.1.1.5 external/ibm-public/postfix/dist/src/postconf/test57.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/postconf/test59.ref up to 1.1.1.4 external/ibm-public/postfix/dist/src/postconf/test67.ref up to 1.1.1.3 external/ibm-public/postfix/dist/src/postconf/test76.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/postdrop/postdrop.c up to 1.6 external/ibm-public/postfix/dist/src/postfix/postfix.c up to 1.8 external/ibm-public/postfix/dist/src/postlog/postlog.c up to 1.7 external/ibm-public/postfix/dist/src/postmap/Makefile.in up to 1.1.1.9 external/ibm-public/postfix/dist/src/postmap/postmap.c up to 1.7 external/ibm-public/postfix/dist/src/postmulti/Makefile.in up to 1.1.1.6 external/ibm-public/postfix/dist/src/postmulti/postmulti.c up to 1.5 external/ibm-public/postfix/dist/src/postqueue/postqueue.c up to 1.6 external/ibm-public/postfix/dist/src/postqueue/showq_compat.c up to 1.5 external/ibm-public/postfix/dist/src/postqueue/showq_json.c up to 1.6 external/ibm-public/postfix/dist/src/postscreen/postscreen.c up to 1.7 external/ibm-public/postfix/dist/src/postscreen/postscreen_endpt.c up to 1.6 external/ibm-public/postfix/dist/src/posttls-finger/posttls-finger.c up to 1.7 external/ibm-public/postfix/dist/src/proxymap/Makefile.in up to 1.1.1.8 external/ibm-public/postfix/dist/src/proxymap/proxymap.c up to 1.6 external/ibm-public/postfix/dist/src/qmgr/Makefile.in up to 1.1.1.7 external/ibm-public/postfix/dist/src/qmgr/qmgr.c up to 1.5 external/ibm-public/postfix/dist/src/qmgr/qmgr_bounce.c up to 1.2 external/ibm-public/postfix/dist/src/qmgr/qmgr_defer.c up to 1.2 external/ibm-public/postfix/dist/src/qmgr/qmgr_message.c up to 1.6 external/ibm-public/postfix/dist/src/sendmail/Makefile.in up to 1.1.1.6 external/ibm-public/postfix/dist/src/sendmail/sendmail.c up to 1.6 external/ibm-public/postfix/dist/src/showq/showq.c up to 1.6 external/ibm-public/postfix/dist/src/smtp/Makefile.in up to 1.1.1.12 external/ibm-public/postfix/dist/src/smtp/lmtp_params.c up to 1.7 external/ibm-public/postfix/dist/src/smtp/smtp.c up to 1.15 external/ibm-public/postfix/dist/src/smtp/smtp.h up to 1.7 external/ibm-public/postfix/dist/src/smtp/smtp_connect.c up to 1.7 external/ibm-public/postfix/dist/src/smtp/smtp_key.c up to 1.4 external/ibm-public/postfix/dist/src/smtp/smtp_params.c up to 1.7 external/ibm-public/postfix/dist/src/smtp/smtp_proto.c up to 1.7 external/ibm-public/postfix/dist/src/smtp/smtp_rcpt.c up to 1.4 external/ibm-public/postfix/dist/src/smtp/smtp_state.c up to 1.5 external/ibm-public/postfix/dist/src/smtp/smtp_tls_policy.c up to 1.6 external/ibm-public/postfix/dist/src/smtp/smtp_tlsrpt.c up to 1.3 external/ibm-public/postfix/dist/src/smtp/smtp_trouble.c up to 1.4 external/ibm-public/postfix/dist/src/smtpd/Makefile.in up to 1.1.1.13 external/ibm-public/postfix/dist/src/smtpd/smtpd.c up to 1.22 external/ibm-public/postfix/dist/src/smtpd/smtpd.h up to 1.7 external/ibm-public/postfix/dist/src/smtpd/smtpd_chat.c up to 1.5 external/ibm-public/postfix/dist/src/smtpd/smtpd_check.c up to 1.8 external/ibm-public/postfix/dist/src/smtpd/smtpd_haproxy.c up to 1.4 external/ibm-public/postfix/dist/src/smtpd/smtpd_peer.c up to 1.6 external/ibm-public/postfix/dist/src/smtpd/smtpd_proxy.c up to 1.4 external/ibm-public/postfix/dist/src/smtpd/smtpd_proxy.h up to 1.2 external/ibm-public/postfix/dist/src/tls/Makefile.in up to 1.1.1.12 external/ibm-public/postfix/dist/src/tls/tls.h up to 1.7 external/ibm-public/postfix/dist/src/tls/tls_client.c up to 1.15 external/ibm-public/postfix/dist/src/tls/tls_dane.c up to 1.7 external/ibm-public/postfix/dist/src/tls/tls_dane.sh up to 1.1.1.2 external/ibm-public/postfix/dist/src/tls/tls_dh.c up to 1.7 external/ibm-public/postfix/dist/src/tls/tls_misc.c up to 1.7 external/ibm-public/postfix/dist/src/tls/tls_prng_file.c up to 1.3 external/ibm-public/postfix/dist/src/tls/tls_proxy.h up to 1.6 external/ibm-public/postfix/dist/src/tls/tls_proxy_client_misc.c up to 1.5 external/ibm-public/postfix/dist/src/tls/tls_proxy_client_print.c up to 1.6 external/ibm-public/postfix/dist/src/tls/tls_proxy_client_scan.c up to 1.6 external/ibm-public/postfix/dist/src/tls/tls_server.c up to 1.14 external/ibm-public/postfix/dist/src/tls/tls_verify.c up to 1.6 external/ibm-public/postfix/dist/src/tls/tlsrpt_wrapper.c up to 1.3 external/ibm-public/postfix/dist/src/tlsproxy/tlsproxy.c up to 1.8 external/ibm-public/postfix/dist/src/tlsproxy/tlsproxy_state.c up to 1.4 external/ibm-public/postfix/dist/src/trivial-rewrite/Makefile.in up to 1.1.1.7 external/ibm-public/postfix/dist/src/trivial-rewrite/resolve.c up to 1.6 external/ibm-public/postfix/dist/src/trivial-rewrite/trivial-rewrite.c up to 1.6 external/ibm-public/postfix/dist/src/util/Makefile.in up to 1.1.1.13 external/ibm-public/postfix/dist/src/util/alldig.c up to 1.4 external/ibm-public/postfix/dist/src/util/argv.c up to 1.6 external/ibm-public/postfix/dist/src/util/argv.h up to 1.6 external/ibm-public/postfix/dist/src/util/dict.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict.h up to 1.7 external/ibm-public/postfix/dist/src/util/dict_alloc.c up to 1.4 external/ibm-public/postfix/dist/src/util/dict_cache.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_cache.h up to 1.3 external/ibm-public/postfix/dist/src/util/dict_cdb.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_cidr.c up to 1.6 external/ibm-public/postfix/dist/src/util/dict_db.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_dbm.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_debug.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_env.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_fail.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_inline.c up to 1.6 external/ibm-public/postfix/dist/src/util/dict_lmdb.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_ni.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_nis.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_nisplus.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_open.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_pcre.c up to 1.6 external/ibm-public/postfix/dist/src/util/dict_pipe.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_random.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_regexp.c up to 1.6 external/ibm-public/postfix/dist/src/util/dict_sdbm.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_seq.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/dict_sockmap.c up to 1.7 external/ibm-public/postfix/dist/src/util/dict_static.c up to 1.5 external/ibm-public/postfix/dist/src/util/dict_surrogate.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_tcp.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_test.c up to 1.3 external/ibm-public/postfix/dist/src/util/dict_thash.c up to 1.6 external/ibm-public/postfix/dist/src/util/dict_union.c up to 1.4 external/ibm-public/postfix/dist/src/util/dict_unix.c up to 1.2 external/ibm-public/postfix/dist/src/util/dict_utf8_test.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/hash_fnv.c up to 1.5 external/ibm-public/postfix/dist/src/util/hex_code.c up to 1.5 external/ibm-public/postfix/dist/src/util/hex_code.h up to 1.6 external/ibm-public/postfix/dist/src/util/htable.c up to 1.5 external/ibm-public/postfix/dist/src/util/inet_addr_list.c up to 1.3 external/ibm-public/postfix/dist/src/util/inet_prefix_top.c up to 1.4 external/ibm-public/postfix/dist/src/util/inet_proto.c up to 1.5 external/ibm-public/postfix/dist/src/util/mac_expand.c up to 1.5 external/ibm-public/postfix/dist/src/util/mac_expand.h up to 1.6 external/ibm-public/postfix/dist/src/util/mac_expand.in up to 1.1.1.5 external/ibm-public/postfix/dist/src/util/mac_expand.ref up to 1.1.1.5 external/ibm-public/postfix/dist/src/util/match_list.c up to 1.4 external/ibm-public/postfix/dist/src/util/midna_domain.c up to 1.6 external/ibm-public/postfix/dist/src/util/mkmap_open.c up to 1.3 external/ibm-public/postfix/dist/src/util/msg_vstream.c up to 1.2 external/ibm-public/postfix/dist/src/util/myaddrinfo.c up to 1.4 external/ibm-public/postfix/dist/src/util/myaddrinfo.h up to 1.5 external/ibm-public/postfix/dist/src/util/myaddrinfo.ref up to 1.1.1.6 external/ibm-public/postfix/dist/src/util/myaddrinfo.ref2 up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/myaddrinfo4.ref up to 1.1.1.3 external/ibm-public/postfix/dist/src/util/myaddrinfo4.ref2 up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/myflock.c up to 1.4 external/ibm-public/postfix/dist/src/util/name_mask.c up to 1.5 external/ibm-public/postfix/dist/src/util/name_mask.h up to 1.2 external/ibm-public/postfix/dist/src/util/name_mask.ref5 up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/name_mask.ref6 up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/netstring.c up to 1.5 external/ibm-public/postfix/dist/src/util/normalize_ws.c up to 1.3 external/ibm-public/postfix/dist/src/util/open_as.c up to 1.2 external/ibm-public/postfix/dist/src/util/open_as.h up to 1.2 external/ibm-public/postfix/dist/src/util/quote_for_json.c up to 1.3 external/ibm-public/postfix/dist/src/util/sane_sockaddr_to_hostaddr.c up to 1.3 external/ibm-public/postfix/dist/src/util/spawn_command.c up to 1.4 external/ibm-public/postfix/dist/src/util/spawn_command.h up to 1.3 external/ibm-public/postfix/dist/src/util/stringops.h up to 1.7 external/ibm-public/postfix/dist/src/util/sys_defs.h up to 1.16 external/ibm-public/postfix/dist/src/util/unescape.ref up to 1.1.1.3 external/ibm-public/postfix/dist/src/util/vbuf_print.c up to 1.6 external/ibm-public/postfix/dist/src/util/vbuf_print_test.in up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/vbuf_print_test.ref up to 1.1.1.2 external/ibm-public/postfix/dist/src/util/vstream.c up to 1.6 external/ibm-public/postfix/dist/src/util/vstream.h up to 1.5 external/ibm-public/postfix/dist/src/util/vstring.c up to 1.5 external/ibm-public/postfix/dist/src/util/vstring_vstream.c up to 1.3 external/ibm-public/postfix/dist/src/verify/verify.c up to 1.6 external/ibm-public/postfix/dist/src/virtual/Makefile.in up to 1.1.1.7 external/ibm-public/postfix/dist/src/virtual/virtual.c up to 1.5 external/ibm-public/postfix/dist/src/virtual/virtual.h up to 1.2 external/ibm-public/postfix/dist/src/xsasl/xsasl_dovecot_server.c up to 1.6 external/ibm-public/postfix/lib/global/Makefile up to 1.12 external/ibm-public/postfix/lib/util/Makefile up to 1.13 external/ibm-public/postfix/libexec/smtp/Makefile up to 1.5 doc/3RDPARTY (manually edited) Import Postfix 3.11.2. @ text @a0 572 Postfix REQUIRETLS Support

Postfix REQUIRETLS Support

Purpose of this document
Introduction
REQUIRETLS for a perimeter MTA
An experiment: testing REQUIRETLS support
Requesting REQUIRETLS without SMTP
Non-delivery notifications
REQUIRETLS quick summary
Credits

Purpose of this document

Introduction

The REQUIRETLS extension in ESMTP is defined in RFC 8689. When a sender requests REQUIRETLS. the message must be sent only over strongly-authenticated SMTP or LMTP connections.

Specifically:

Every server in the forward path to the final destination must announce REQUIRETLS support.

Challenge: as of 2025, only a few servers implement REQUIRETLS.
Every server in the forward path must be looked up securely (for example, with DNSSEC or HTTPS).
Every server certificate in the forward path must be verified. In practice, this involves DANE (+DNSSEC) or MTA-STS; custom configuration would not scale.

Challenge: as of 2025, many domains do not publish a DANE or MTA-STS policy.
A message with REQUIRETLS must be returned to the sender if any of the above requirements is not satisfied (no STARTTLS support, no secure server lookup, no trusted or no matching server certificate, or no server that announces REQUIRETLS support).

For more background information, see the REQUIRETLS quick summary below.

REQUIRETLS for a perimeter MTA

Receiving inbound messages with REQUIRETLS requests

Postfix has one global parameter setting that controls REQUIRETLS support in all Postfix processes. The default setting is:

/etc/postfix/main.cf:
    requiretls_enable = yes

NOTE: The configuration below may be suitable for a personal domain, where the owner can decide what happens with all messages. For domains that receive messages for other people, a less radical approach may be better, as described in the sections that follow.

1 /etc/postfix/main.cf:
2     # Don't enforce REQUIRETLS when delivering mail with SMTP or LMTP.
3     smtp_requiretls_policy = opportunistic
4     lmtp_requiretls_policy = opportunistic
5     
6     # Don't detect or add a "Require-TLS-ESMTP: yes" header.
7     requiretls_esmtp_header = no

Lines 3-4: These relax REQUIRETLS enforcement when delivering a email to a message store, content filter, or other destination that may not support REQUIRETLS. If a server does not support STARTTLS or REQUIRETLS, then Postfix will simply deliver the message as if the sender did not request REQUIRETLS.
Line 7: The requiretls_esmtp_header feature enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter based on SMTPD_PROXY_README or FILTER_README. This feature can safely be disabled if the domain does not need to enforce REQUIRETLS while delivering or forwarding messages.

LMTP and SMTP-based message stores and content filters

opportunistic: STARTTLS and REQUIRETLS support are optional. When the sender requests REQUIRETLS, and an SMTP or LMTP server supports STARTTLS and REQUIRETLS, then send REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.

For a more complete definition of this enforcement level, see the smtp_requiretls_policy parameter documentation.

For REQUIRETLS, the relevant Postfix 3.11 configuration default settings are:

 1 /etc/postfix/main.cf:
 2     smtp_tls_security_level = may
 3     requiretls_esmtp_header = yes
 4     lmtp_requiretls_policy = opportunistic
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13       ...to be completed in section "Communication with external servers"...

Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.

Non-SMTP and non-LMTP content filters

Postfix FILTER_README describes content inspection based on a pipe-to-command approach. For REQUIRETLS, the relevant Postfix 3.11 default setting is:

/etc/postfix/main.cf:
    requiretls_esmtp_header = yes

Communication with external servers

For communication with external servers, the Postfix SMTP client supports multiple enforcement levels:

enforce: When the sender requests REQUIRETLS, require secure lookup of MX hosts (for example, using DNSSEC or HTTPS), require a server certificate match (for example, based on a published DANE or STS policy), and require that the remote server supports REQUIRETLS. Otherwise return the message as undeliverable.

NOTE: this is also used implicitly when no REQUIRETLS policy match is found.
opportunistic+starttls: When the sender requests REQUIRETLS, require that the server supports STARTTLS. Send REQUIRETLS if the server supports REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.
opportunistic: STARTTLS and REQUIRETLS support are optional. When the sender requests REQUIRETLS, and an SMTP or LMTP server supports STARTTLS and REQUIRETLS, then send REQUIRETLS, otherwise simply deliver the message as if the sender did not request REQUIRETLS.

For a more complete definition of these enforcement levels, see the smtp_requiretls_policy parameter documentation.

For sending mail with REQUIRETLS, the relevant Postfix 3.11 default settings are shown below, with one suggested setting in a comment (line 2).

 1 /etc/postfix/main.cf:
 2     # smtp_tls_policy_maps = ...dane/sts plugin...
 3     smtp_tls_security_level = may
 4     requiretls_esmtp_header = yes
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13         enforce

New at line 13: The 'enforce' policy for external destinations is technically correct, but is likely to suffer from delivery failures because many domains do not publish a DANE or STS policy, and many MTAs support STARTTLS but not REQUIRETLS. A perhaps more practical policy may be found in the section Relaxing REQUIRETLS for external deliveries.
(Same as before) Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
(Same as before) Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
(Same as before) Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
(Same as before) Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.)

Relaxing REQUIRETLS for external deliveries

 1 /etc/postfix/main.cf:
 2     smtp_tls_security_level = may
 3     # smtp_tls_policy_maps = ...dane/sts plugin...
 4     requiretls_esmtp_header = yes
 5     smtp_requiretls_policy =
 6         inline:{
 7             { ${domain_to_ascii{$mydomain}} = opportunistic }
 8             { .${domain_to_ascii{$mydomain}} = opportunistic }
 9             { localhost = opportunistic } }
10         cidr:{
11             { 0.0.0.0/0 opportunistic }
12             { ::/0 opportunistic } }
13         opportunistic+starttls

New at line 13: the 'opportunistic+starttls' policy relaxes the requirement that every MTA in the forward path of a message supports REQUIRETLS, but in practice only one network hop needs to be secured: from a sender's perimeter MTA to a receiver's perimeter MTA. The network connections between user agents and their respective perimeters are assumed to be already secure.
(Same as before) Line 3: The requiretls_esmtp_header setting enables support for a message header "Require-TLS-ESMTP: yes" that allows Postfix to propagate the sender's REQUIRETLS request through a content filter. This feature can safely be disabled if there is no need for content inspection based on SMTPD_PROXY_README or FILTER_README.
(Same as before) Lines 5-12: These make REQUIRETLS support optional for internal destinations and content filters that are specified as a symbolic name (lines 6-9) or as a numerical IP address (lines 10-12).
(Same as before) Lines 7 and 8 use ${domain_to_ascii{$mydomain}} instead of $mydomain. The function domain_to_ascii{} returns $mydomain if that contains only (7-bit) ASCII. If the mydomain value contains non-ASCII characters, then domain_to_ascii{} returns the xn--mumble-mumble Punycode (A-label) form that Postfix needs. This works around a limitation that may be eliminated in a future Postfix version.
(Same as before) Note: if you specify a domain list outside main.cf, then the automatic $name expansions and Punycode conversions will not happen; you will need to enter real domain names and will need to convert non-ASCII domains to Punycode.)

An experiment: testing REQUIRETLS support

Requesting REQUIRETLS without SMTP

There are two options:

Specify the Postfix-specific "sendmail -Orequiretls=yes" command-line option. This option is always available, but may not be convenient to use.
Add a Postfix-specific "Require-TLS-ESMTP: yes" message header. This is easier to use, but requires the setting "requiretls_esmtp_header = yes" which is not recommended for systems without content filters based on SMTPD_PROXY_README or FILTER_README.

Question: perhaps there needs to be a parameter setting to request REQUIRETLS for specific email sources or contexts?

Non-delivery notifications

By default, Postfix redacts an undeliverable REQUIRETLS message as described in RFC 8689, before returning it to the sender:

Remove the label "this message needs REQUIRETLS". The purpose is to avoid loss of notifications when a reverse path does not support REQUIRETLS, even though the forward path supported it.
Return only the message header, as if the message was received with the RFC 3461 DSN option "RET=HDRS". The purpose is to limit the amount of information that may be exposed in plaintext.

The relevant default setting is:

/etc/postfix/main.cf:
    requiretls_redact_dsn = yes

When a message was received with a "TLS-Required: no" header, and REQUIRETLS was not requested, the "TLS-Required: no" header is copied to the delivery status notification.

REQUIRETLS quick summary

The REQUIRETLS extension in ESMTP allows a sender to request that a message will be sent over connections that are protected with TLS. RFC 8689 defines two SMTP features:

A message header "TLS-Required: no" that disables TLS enforcement: do not require a server certificate match, and allow falling back to plaintext if TLS is unavailable. This may be useful to report a TLS problem, as described in TLSRPT_README. This feature has lower precedence than REQUIRETLS, and is not discussed further in this document.
An ESMTP protocol extension named "REQUIRETLS" that an SMTP server may list in its EHLO response, and that an SMTP client may request in a MAIL FROM command. This extension can be used only in an encrypted session, as illustrated with the fragment below, where C=client and S=server.
```
. . .
C: STARTTLS
S: 220 Ready to start TLS
C: EHLO client.example.org
S: 250-mail.example.com 
   . . .
   250 REQUIRETLS
C: MAIL FROM:<sender@@example.org> REQUIRETLS
S: 250 OK
. . .
```
RFC 8689 applies equally to message relay [RFC 5321], submission [RFC 6409], and the LMTP Local Mail Transfer Protocol [RFC 2033].
REQUIRETLS is an end-to-end feature, unlike SMTP which is hop-by-hop. When a sender requests REQUIRETLS, each server in the forward path must support REQUIRETLS.
Each connection in the forward path must be made to a server that has been looked up securely (for example, with DNSSEC or HTTPS).
Each server certificate must be verified. To match a server certificate, the Postfix SMTP client needs to use an appropriate policy type:
- A TLS policy type 'secure' or 'verify', with certificate name matching info. For example, a policy returned by an MTA-STS plugin that looks up certificate matching info using HTTPS;
- A TLS policy type 'dane-only', which looks up certificate or public-key matching info using DNSSEC. For example, a policy that is returned by a DANE+STS plugin;
- A TLS policy type 'dane', provided that both the nexthop domain and its MX hosts are in DNSSEC-signed zones, and usable DNSSEC-signed TLSA records are discovered. In other words, the effective TLS policy remains DANE and is not downgraded because the destination lacks DNSSEC and/or usable TLSA records;
- A TLS policy type 'fingerprint', with digital fingerprints. This is a non-scalable solution for special deployments, mentioned here only for completeness.
A message that requires REQUIRETLS must be returned to the sender if any of the above requirements is not satisfied (no STARTTLS support, no secure lookup of MX servers, no trusted or no matching server certificate, or no server that announces REQUIRETLS support).
Returning an undeliverable message that requires REQUIRETLS comes with its own challenges: the return path may differ from the forward path, and the return path may not support REQUIRETLS all the way back to the sender, even if the forward path supported REQUIRETLS. By default, Postfix follows RFC 8689 and redacts bounce messages so that they can be sent without REQUIRETLS.

Credits

In Postfix 3.10, Wietse Venema refactored SMTPUTF8 support and extended it to propagate REQUIRETLS and "TLS-Required: no" information.
In Postfix 3.11, Wietse added REQUIRETLS support to the Postfix SMTP client; added a "tls=status/requiretls=status" field to the Postfix delivery status logging; added smtp_requiretls_policy support; added support for the "Require-TLS-ESMTP: yes" header to propagate REQUIRETLS through non-Postfix programs, specifically content filters.

Postfix REQUIRETLS Support

Table of Contents

Purpose of this document

Introduction

REQUIRETLS for a perimeter MTA

Receiving inbound messages with REQUIRETLS requests

LMTP and SMTP-based message stores and content filters

Non-SMTP and non-LMTP content filters

Communication with external servers

Relaxing REQUIRETLS for external deliveries

An experiment: testing REQUIRETLS support

Requesting REQUIRETLS without SMTP

Non-delivery notifications

REQUIRETLS quick summary

Credits

Postfix REQUIRETLS Support

Table of Contents

Purpose of this document

Introduction

REQUIRETLS for a perimeter MTA

Receiving inbound messages with REQUIRETLS requests

LMTP and SMTP-based message stores and content filters

Non-SMTP and non-LMTP content filters

Communication with external servers

Relaxing REQUIRETLS for external deliveries

An experiment: testing REQUIRETLS support

Requesting REQUIRETLS without SMTP

Non-delivery notifications

REQUIRETLS quick summary

Credits