Mailman 2.1.29 shipped with limited DMARC compatibility. This was improved significantly with Mailman 2.1.30. As a result, the Mailman version in Red Hat Enterprise Linux is currently of limited use. An isolated patch which should have the same effect (with suitable list configuration) is available here: https://launchpad.net/mailman/+milestone/2.1.30 For background, please refer to this discussion: https://sourceware.org/bugzilla/show_bug.cgi?id=29713#c6 Testing of this patch with a google.com-to-Gmail message flow is still under way.