This is not a security issue in Mailman. Yes it is possible to spoof a list member's address in various headers to cause a post to be accepted by a list, but there's nothing Mailman or any list management software can do about that short of moderating all members. Also, see <https://mail.python.org/pipermail/mailman- users/2017-October/082558.html>, <https://wiki.list.org/x/4030556> and the "How to post to the announcement list:" section at <https://wiki.list.org/x/4030685>. ** Changed in: mailman Status: New => Invalid -- You received this bug notification because you are a member of Mailman Coders, which is subscribed to GNU Mailman. https://bugs.launchpad.net/bugs/1721746 Title: [If member-email known] Malformed "From:" header accepted -> anyone can post to list. To manage notifications about this bug go to: https://bugs.launchpad.net/mailman/+bug/1721746/+subscriptions