Mac Mail - Outlook Exchange issues

Occasional Contributor

I'm having a weird issue with my Outlook, 365, Exchange account in Mac Mail. This only started being a problem in the last two day. My inbox won't refresh. New messages don't come in. Messages filed or deleted on another Mac or iPhone do not move/remove. 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. I can send just fine. Clicking in to folders seems just fine as far as showing and matching what is inside. Its JUST a problem with the Inbox never updating without support. 


The Mac Pro having the problem is on 10.15.7. 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. 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. 


I need to hold off on updating the Pro to Big Sur just yet so hoping to get a fix until then.

12 Replies



Hi, I know it's not necessarily the answer you will be looking for, but as a fellow mac user, I find M365 mail accounts work much better with Outlook. 


If it turns out that the upgrade to the latest Mac OS does indeed solve this for you, then trying Outlook until you update the Mac could be a workaround for you perhaps?

Best Response confirmed by commanderclif (Occasional Contributor)



Well, for whatever its worth it just went back to working again. Not sure if it was a Microsoft issue or an Apple issue but Exchange account/Mac Mail - Catalina is working just fine again.



I have seen this behaviour both on Catalina and Big Sur multiple times: My incoming email from my Office 365 account is not shown in Apple Mail. Sometimes a Mailbox->Rebuild make them show themselves, but sometimes this doesn't work. It fixes itself after some time (once it took several days, yesterday it took around 24 hours). I saw even consistent behaviour and same timing on both my iMac and my MacBook (running Big Sur 11.1 for two weeks now). Outlook for Mac on both boxes however showed all incoming email from the same account just in time when they arrived.


So my guess it is interworking issue between Apple Mail and the Exchange part of Office 365, but only intermittently, but still repeating. No idea here to further track this down.



Thanks for adding your experience! I hope we can track it down at some point to pinpoint what the issue is and if there is something that can be done to fix it right away. I stopped having issues but since I've seen it more than once I know it can come back at any point. 




I just did some research: Problem is not occurring on a clean Big Sur MacBook Pro... One suspect could be Little Snitch - do you have this installed on your system?

@pradig I don't use Little Snitch so I don't think that is the issue. When I was having the issue it was on two macs and my thought at the time was that MS had made a change (or Apple, but there hadn't been an update recently, just one day it worked the next it didn't).  I'm not complaining that within two days of the problem starting it stopped, and stopped on both Macs at the same time and I can't say I've seen the problem occur since. Fingers crossed it stays working and whatever "switch" someone flicked, doesn't get switched again!



I'm experiencing it as well - making Big Sur Mail.App effectively useless - restarting it every time I want to pull email that I see on my iOS devices. I only get the sync with O365 once, right after restarting


I wonder if it is because I was on public beta, and Big Sur was installed as an upgrade, not a clean install. What a PITA if that's the only solution. 



I never had the beta version installed, went straight from 10.15.7 to 11.1 and still saw the problem on both versions.

I have the same issues, btw. I have to restart Mac Mail to make it load new messages. If I click Get Mail, it says Checking for Mail in the Activity window and chugs for a moment, but doesn't find any email even though my phone did. 





This is happening to you right now? I've been curious if it happens to everyone at once, or to individual users sporadically. I am not having an issue right now. 

@commanderclif Yes, now. 

I worry that it's that I have big an inbox in 365. It's 9GB with ~50K messages. But it hasn't been a problem before. 



For what it is worth, my account size is 8.37 GB with 25,188 msgs. Don't think its connected to account size since I've not had this problem occur since my last issue back in November (to the best of my knowledge but of course it could have happened while I was away from the office during the holidays.)