How's this (from src/mailman/mta/docs/authentication.txt) The SMTP server may require authentication. Mailman supports setting the SMTP user name and password. The actual authentication mechanism used is controlled by Python's `smtplib module`_, which tries `CRAM-MD5` first, followed by `PLAIN` and `LOGIN`. When sending authentication data between Mailman and the MTA over an unsecured network, the submission (mail) server should support `CRAM-MD5`. -- You received this bug notification because you are a member of Mailman Coders, which is subscribed to GNU Mailman. https://bugs.launchpad.net/bugs/490044 Title: Implement SMTP AUTH in Mailman 3