I upgraded to the new Apple operating system High Sierra and now I can't receive mail using MacOS Mail and my Office 365 account? Help!
I was helping a friend that has an Mac and they upgraded to High Sierra. They then went to MacOS Mail (the stamp icon) to access their email. They had two email accounts. One of which was with Office 365.
They noticed that some mail they were expecting hadn't arrived. So they used their browser to access the mail and the mail had come in. So why didn't MacOS Mail find it?
When I did some searching and found that since the High Sierra upgrade Apple broke MacOS MAIL and it was not working correctly with Office 365 accounts. At this time the problem does not affect all Office 365 accounts.
Apple and Microsoft are chatting about the problem. Wouldn't you like to be a fly on that wall?
The only options you have at this point is to wait and use your browser, or install one of many free or not free mail applications like Thunderbird, or Outlook. Apple says they will fix it but I wouldn't hold my breath.