This is a non-trivial problem. I've spent nearly 3 hours in chat with Google Support. This escalated to 2nd level and then internal support. It may be related to SMTP servers bouncing messages.
I am not actually expecting a resolution from this message. What I hope is some SMTP admins can make suggestions on how to get more information to resolve this issue. Something with which I can prod Google Internal Support team.
We have a Google Workspace for Business and are using multiple Groups.
Summary of issue for our Members group:
- Msg received from certain users, like myself.
- Msg is posted to group website conversation.
- Msg is 'bounced' per Email Log in Workspace.
Quirks of issue:
- Msgs from most users are processed through to members of Group.
- Msgs from users that bounce in Members do not bounce in other groups.
- All groups are configured the same.
- Msg content, not the user, may be the problem but I can't identify common aspects. Especially across multiple domain SMTP servers as mentioned in next item.
- Google suggests it is the domain SMTP server for recipient user's email that is bouncing the message. That may be correct but emails are being bounced by servers for gmail.com, att.net, comcast.net and a few others. That seems strange. No suggestion on why these diverse servers would all reject the emails.
The log entry appears as:
Aug 19, 2022, 3:27:54 PM Forwarded from group: members@domain.org
Aug 19, 2022, 3:27:54 PM Accepted from group forwarding
Aug 19, 2022, 3:27:54 PM Bounced Message rejected. See https://support.google.com/mail/answer/69585 for more information.
For a non-bounce the 3rd line says 'Delivered'. My understanding (guess?) of the sequence is:
'msg' >> [smtp servers] >> [group server] >>
[google smtp] >> [users smtp] >> user
^ {bounce}
My suspicion is there is another Google server involved that is doing the bounce and not the [users smtp] server.
I have dumped the email log to a spreadsheet which shows more details on the processing sequence. It doesn't provide any usable info as far as I can tell.
Any suggestions on resolving this?
Update: Is there an SMTP server online where I can see the logs? I could create a users in the Group for that server. If a message bounces logs on the SMTP server should show why.
Update 2022/8/24: As stated in comment sent msg from group web interface to Mail Genius. It didn't bounce. A msg sent from my personal account showed Google mail servers spam blacklisted. Forwarding results to Google support.