Public bug reported: Mailman tarballs contain a Defaults.py file with this configuration: DEFAULT_PASS_MIME_TYPES = ['multipart/mixed','multipart/alternative','text/plain'] NOTE: I don't know how this file is generated, I found it on the tarballs but not on the repository So, when someone enables filtering on a mailing list by mime-type, the default is to filter all emails not matching any of those 3 mime-types. This list of default mime types allowed misses to include "multipart/signed". Therefore, this is unfortunately filtering any "multipart/signed" emails. "multipart/signed" is defined on RFC 3156 <https://tools.ietf.org/html/rfc3156> and is the recommended way of signing mails with GPG. See http://wiki.gnupg.org/SignatureHandling The proposed change is to modify that default configuration to: DEFAULT_PASS_MIME_TYPES = ['multipart/mixed', 'multipart/alternative', 'multipart/signed', 'text/plain', ] This default causes trouble to people that signs their mails with GPG. I already had problems due to this default on the Alioth Debian mailing lists and on the WebKit mailing lists because the admin enabled filtering by mime-type and didn't changed the default. Please, change this default by adding at least 'multipart/signed' to the list of types allowed. ** Affects: mailman Importance: Undecided Status: New -- You received this bug notification because you are a member of Mailman Coders, which is subscribed to GNU Mailman. https://bugs.launchpad.net/bugs/1517446 Title: Please add multipart/signed to DEFAULT_PASS_MIME_TYPES To manage notifications about this bug go to: https://bugs.launchpad.net/mailman/+bug/1517446/+subscriptions