[Pkg-mailman-hackers] Bug#1060423: Postfix integration instructions appear to be erroneous

[Rob Leslie]

Package: mailman3
Version: 3.3.8-2~deb12u1
Severity: normal
File: /usr/share/doc/mailman3/README.Debian

Dear Maintainer,

The instructions for integrating Mailman3 with Postfix include the
following Postfix configuration parameters:

transport_maps = hash:/var/lib/mailman3/data/postfix_lmtp
local_recipient_maps = proxy:unix:passwd.byname $alias_maps hash:/var/lib/mailman3/data/postfix_lmtp
relay_domains = ${{$compatibility_level} < {2} ? {$mydestination} : {}} hash:/var/lib/mailman3/data/postfix_domains

However, this appears to be inconsistent and can lead to a situation
where messages addressed to invalid recipients in the Mailman3 domains
are rejected with a mail "loops back to myself" message rather than a
more appropriate "User unknown". This is because local_recipient_maps is
only checked for recipient addresses in the local domain class (e.g.
domains listed in the mydestination parameter) and not for recipient
addresses in the relay domain class (relay_domains).

I believe it is more appropriate to use relay_recipient_maps instead of
local_recipient_maps together with relay_domains, e.g.:

transport_maps = hash:/var/lib/mailman3/data/postfix_lmtp
relay_recipient_maps = hash:/var/lib/mailman3/data/postfix_lmtp
relay_domains = ${{$compatibility_level} < {2} ? {$mydestination} : {}} hash:/var/lib/mailman3/data/postfix_domains

This configuration causes messages with invalid recipients in the
Mailman3 domains to be properly rejected with "User unknown".


-- System Information:
Debian Release: 12.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-17-amd64 (SMP w/2 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages mailman3 depends on:
ii  cron                         3.0pl1-162
ii  dbconfig-mysql               2.0.24
ii  dbconfig-sqlite3             2.0.24
ii  debconf [debconf-2.0]        1.5.82
ii  init-system-helpers          1.65.2
ii  logrotate                    3.21.0-1
ii  python3                      3.11.2-1+b1
ii  python3-aiosmtpd             1.4.3-1.1
ii  python3-alembic              1.8.1-2
ii  python3-authheaders          0.15.2-1
ii  python3-authres              1.2.0-3
ii  python3-click                8.1.3-2
ii  python3-dateutil             2.8.2-2
ii  python3-dnspython            2.3.0-1
ii  python3-falcon               3.1.1-1+b1
ii  python3-flufl.bounce         4.0-3
ii  python3-flufl.i18n           3.0.1-3
ii  python3-flufl.lock           5.0.1-4
ii  python3-gunicorn             20.1.0-6
ii  python3-importlib-resources  5.1.2-2
ii  python3-lazr.config          2.2.3-3
ii  python3-passlib              1.7.4-3
ii  python3-public               2.3-4
ii  python3-pymysql              1.0.2-2
ii  python3-requests             2.28.1+dfsg-1
ii  python3-sqlalchemy           1.4.46+ds1-1
ii  python3-zope.component       5.1.0-1
ii  python3-zope.configuration   4.4.1-1
ii  python3-zope.event           4.4-3
ii  python3-zope.interface       5.5.2-1+b1
ii  ucf                          3.0043+nmu1

Versions of packages mailman3 recommends:
ii  postfix [mail-transport-agent]  3.7.9-0+deb12u1

Versions of packages mailman3 suggests:
pn  anacron                                <none>
ii  lynx [www-browser]                     2.9.0dev.12-1
pn  mailman3-doc                           <none>
ii  mariadb-server [virtual-mysql-server]  1:10.11.4-1~deb12u1

-- debconf information excluded