As an aside: If you have a 30 Gig mailbox with a lot of items AppleMail takes days to get caught up and yes I don't downlead ANY attachments or store items on the server. Got a brand new MacBook Pro out of a box top end, 32 GB that's all we use ( not M1 yet) and rebuilt it and 4 days later same thing. On Catalina, I did my usual archiving and clean build and all 80,000 emails downloaded and it was working smoothly then it just stopped again.ģ. I need to hold off on updating the Pro to Big Sur just yet so hoping to get a fix until have you found a solution to this issue? I run into this once a year or every 6 months depending on email volumes when the mailbox size or mail count goes over a 'certain' size. So seems to only be a Catalina issue but I'm nearly 100% sure it was a problem before I updated the Mac Pro to 10.15.7 yesterday.

My MacBook Pro Late 2019 running the same OS was having the problem all day yesterday but it has since be updated to Big Sur and now is working correctly. The Mac Pro having the problem is on 10.15.7. Its JUST a problem with the Inbox never updating without support. Clicking in to folders seems just fine as far as showing and matching what is inside. The only way I can get the Inbox to fresh to match my other devices, including the browser window version is to go Rebuild under the Messages menu in Mac Mail. Messages filed or deleted on another Mac or iPhone do not move/remove. This only started being a problem in the last two day.

I'm having a weird issue with my Outlook, 365, Exchange account in Mac Mail.

Mac mail exchange gui