Got this message from support: -------- Forwarded Message -------- Hi Evan, This is a new one for us. The recent upgrade to Mailman 2.1.20 has thrown a few curved balls. We spinning up a new test list just now, on the server that you are on, to confirm that it's not happening system wide. We're also going to be testing on a few different email applications to see if there is a problem there. My apologies for the grief. And I hope to have a resolution in the next couple of hours.