Public bug reported: According to rfc2919 the List-Id field should be formated like this: list-id-header = "List-ID:" [phrase] "<" list-id ">" CRLF This works as long as description is left blank or contains supported characters. In my case the description was as follows: �ffentliche Supportliste As you can see the umlaut "Ö" got broken while importing the list from an old server. Unfortunately I don't know how the import was done. The field is still present but < and > around the list-id are missing. This is problematic with procmail and other mail filters. ** 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/1831321 Title: the List-Id field is filled without < and > around the list-id if the description contains unsupported characters To manage notifications about this bug go to: https://bugs.launchpad.net/mailman/+bug/1831321/+subscriptions