mail: Postfix notices to postmaster are silently lost

[stephdl]

Postfix sends its own notices (classes resource and software by default) to the bare address postmaster. With myorigin = <host>.localhost this becomes postmaster@<host>.localhost, which does not resolve in any map. The notice bounces and, since it uses the null sender, it is silently discarded. Nobody is told when Postfix hits a resource or software problem.

Steps to reproduce

• Install mail 1.8.0, bind it to a user domain (Samba AD or OpenLDAP) and add a mail domain
• Enter the postfix container: runagent -m mail1 podman exec -ti postfix sh
• Send a message to the bare postmaster address: printf 'Subject: test\n\ntest\n' | sendmail -f '' postmaster
• Check the journal: journalctl --since -2min | grep status=

Expected behavior

The message is delivered to the postmaster public mailbox, like mail sent to postmaster@<mail domain>.

Actual behavior

to=<postmaster@mail.example.org.localhost>, orig_to=<postmaster>, ... dsn=5.1.1, status=bounced (... 550 5.1.1 <postmaster@mail.example.org.localhost> User doesn't exist ...)

The wildcard alias postmaster@* -> vmail+postmaster only applies to domains in the domains table. The internal .localhost domain is not listed there.

A possible fix is to map postmaster@<host>.localhost to vmail+postmaster, next to the existing inline vmail@<host>.localhost entry. Enabling bounce and 2bounce in notify_classes, or making it a setting, could also be considered.

Components

• ns8-mail 1.8.0, latest stable release
• Reproduced on a test system with Samba AD and OpenLDAP, same code in current main

See also

• Reported by Thorsten, private message