On Apr 27, 2020, at 11:21 AM, Bruce Johnson <johnson@pharmacy.arizona.edu> wrote:
I am not sure how to figure this out.
Lengthy explanation:
Internally in our Exchange server, that address is a distribution group whose only member is the actual <list-name>@lists.pharmacy.arizona.edu, because the Mailman server is not our mail server. (we have a mildly complicated setup: hybrid OnPrem and O365 exchange + Barracuda spam appliance in front of all of it, which is our actual SMTP server.
Outgoing email from the list server bypasses Exchange and is sent directly to the Barracuda SMTP server.
For two users and ONLY these two users, somewhere between them and mailman and back, the Mailman list is being expanded to put all the members of the list on the CC line. It then gets held for approval with a ’too many addresses’ message.
Just posting this for the record in case any other person is unlucky enough to run into this…it turns out that the culprit in this case was the Zoom Outlook plug-in, when dealing with changing, deleting or adding to existing scheduled meeting instances (for instance biweekly faculty meetings were originally scheduled and sent as outlook invites to the mailman list. I finally caught how this was happening when another one of our people ran into it and noticed it only happened to the messages that had to do with Zoom meetings.
I do not know the full details of the issue yet, but I'm guessing that Zoom tried to be oh-so-clever, went back to THEIR servers, retrieved and appended the email addresses for the people who had logged into the meetings associated with that Exchange event record in the past. Altering or deleting a simple calendar event in Exchange does not do this, so it’s not anything on the Exchange side of things.
There appears to be no way of changing this on a quick perusal of the settings and Zoom is retiring the outlook plugin for a different architecture built into O365, I do not know yet if it continues the bug, but I'm sure I’ll find out as our entire campus is heavily invested in both Outlook and Zoom especially this fall.
-- Bruce Johnson University of Arizona College of Pharmacy Information Technology Group
Institutions do not have opinions, merely customs