Currently, whenever Mailman delivers a message to a list, a list-specific `Sender' header is appended. As RFC822 specifies that there should only be at most `Sender' header in any message, appending is not right if there already is such a header present (e.g. whenever the senders MUA added a `Sender' header). The included (untested, but simplistic) patch (against current CVS Mailman) tries to fix this. [ However, I suspect my patch might not work for messages already containing multiple `Sender' headers when Mailman receives them, as Message.SetHeader doesn't appear to really be "crushing duplicates" in those cases. ] To cater for umbrella lists, similar fixes should probably be applied to the `Errors-To' and `X-Mailman-Version' header appending in Mailman.Deliverer.DeliverToList(). -- Harald --- Mailman/Deliverer.py.orig Sun Nov 29 22:12:12 1998 +++ Mailman/Deliverer.py Sun Nov 29 22:11:17 1998 @@ -110,7 +110,7 @@ if self.reply_goes_to_list: del msg['reply-to'] msg.headers.append('Reply-To: %s\n' % self.GetListEmail()) - msg.headers.append('Sender: %s\n' % self.GetAdminEmail()) + msg.SetHeader('Sender', self.GetAdminEmail()) if not msg.getheader('list-id'): msg.headers.append('List-Id: %s\n' % self.GetListIdentifier()) msg.headers.append('Errors-To: %s\n' % self.GetAdminEmail())