On 11/01/2017 09:19 AM, Nick Wyman wrote:
I now think this is due to a spam email which was sent to firstname.lastname@example.org (it's stuck in my mail queue) which is somehow erroneously being processed by mailman and routed to this particular list's owners, but with a bad sender address.
Do you have a copy of this spam email including all headers? That might be helpful.
Also, what happens if you send a message to mailman-owner@... ?