Hi Ned,
I’d like to collect more information about the issue:
1. Did the issue occur to all the messages or some specific users?
2. Do other users encounter the issue?
3. Are you using Office 365 pre-upgrade or after-upgrade? Please see Am I using Office 365 after the service upgrade?
4 . Are you connecting to Office 365 via POP connection?
5. Could you provide the Service Request number so that I can check the status of it?
To protect your privacy, I have sent you a private message to require the information. Here are the steps to access the private message :
1. Please go to Your details section on the right side of the community site.
2. Click Private messages.
3. Click the subject title to read the message and reply with your information.
Best Regards,
Bruce Zhou