Q: Mailman does not work with Postfix, complaining about GID mismatch
A: Mailman uses a setgid wrapper that is designed to be used in
system-wide aliases file so that rest of mailman's mail handling
processes will run with proper uid/gid. Postfix has an ability to run a
command specified in an alias as owner of that alias, thus mailman's
wrapper is not needed here. The best method to invoke mailman's mail
handling via aliases is to use separate alias file especially for
mailman, and made it owned by mailman and group mailman. Like:
alias_maps = hash:/etc/postfix/aliases, hash:/var/mailman/aliases
Make sure that /var/mailman/aliases.db is owned by mailman user (this
may be done by executing postalias as mailman userid).
Next, instead of using mailman-suggested aliases entries with wrapper,
use the following:
instead of
mailinglist: /var/mailman/mail/wrapper post mailinglist
mailinglist-admin: /var/mailman/mail/wrapper mailowner mailinglist
mailinglist-request: /var/mailman/mail/wrapper mailcmd mailinglist
...
use
mailinglist: /var/mailman/scripts/post mailinglist
mailinglist-admin: /var/mailman/scripts/mailowner mailinglist
mailinglist-request: /var/mailman/scripts/mailcmd mailinglist
...