I just spent the morning dealing with all sorts of odd problems relating to configuring Mailman, a mailing listserver, with Gentoo Linux and Postfix. Most of the process went very smoothly up until the actual testing which yielded errors.
The first problem is the way that the Gentoo software installation system (portage) installs Mailman vs. the way Mailman recommends the installation of Mailman. Mailman default installation from source places all the scripts, mailing lists and queues in /var/mailman. Gentoo puts the mailing lists and configurations in /var/lib/mailman and the binaries and scripts into /usr/lib/mailman.
The configuration of postfix went fine as I pointed to the postfix-to-mailman.py script where I put it (/usr/lib/mailman/bin). You have to get the postfix-to-mailman.py script separately from mailman.org.
The postfix-to-mailman.py script has two variables at the top: MailmanHome and MailmanOwner. I set the MailmanHome to /var/lib/mailman which was right. However, the postfix-to-mailman.py script looks for the “mailman” script to be in /var/lib/mailman/mail/mailman. That turned out to be incorrect for gentoo because the scripts are in /usr/lib/mailman. to that end, I added a variable called MailmanBinHome on the line after MailmanHome and set it to /usr/lib/mailman.
I changed MailmanHome on lines 107 and 108 to MailmanBinHome and voila, everything started working.