Mac Mail - Outlook Exchange issues

Copper 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.

41 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 (Copper 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.)

@commanderclif hello 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. 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. 

2. Tried Big Sur it does the same thing,

3. 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. 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. Not sure why Outlook can download a 60Gb MB in less than a day and useable immediately where AppeMail is pretty useless until ALL of the old emails downloads. I think Outlook does pointers and only the new emails first.


Of course:


1. Rebuild mailbox gets all new mail

2. Open and closing the client does them same sometimes.

3. Deletion and sending new email still work normally.


Same issue everyone else sees "checking mail. No new mail"  when in fact there are many I see on webmail and Outlook. Or it does nothing no activty in activty montor or in mail client WIndows Activity


They have a strong dislike for Outlook but of course Outlook and EAS ALWAYS works. So they have to use Outlook while Apple addresses the issue.


Apple can you please see what's going on because something has changed. It is not end user error here for all of us.





@bradw2021 @commanderclif 


I have a user experiencing the same exact issues. OS 11.1

- Inbox will not refresh on command. Requires a rebuild to get new messages.

-Send & delete work fine

-No errors on connection doctor

Please let me know if you find a solution for this.

@tyler706  Exact same issue here. m1 MacBook air. The only way to get my new messages to download is to uninstall the exchange account and reinstall and it downloads about 50 of the most recent then stops.



Thanks for your post and good information here! Your 3 bullet points of work arounds are spot on to what I noticed when I was having the issue. I've not had issues since November but now we seem to be seeing some connection to account size and the problem. I initially brushed that off as being a possible cause of the issue since mine seemed to fix itself as mysteriously as it started. BUT now that I think about HOW this might have played out is my settings are to erase deleted messages and junk messages "after one month". So there is a possibility that my trash had gotten overloaded with huge attachments that tipped that scale. IF/WHEN it occurs to me again I will certainly pull my account size to see if that helps determine a starting point account size capping. Best estimate at this point seems to be 9GB. 

I too prefer Mac Mail to Outlook as an app. I'd be curious if in your case you are saving more than a month, like never empty. In which case, does dumping a bunch of trash does that immediately fix the problem? Obviously this can only be tested by someone who is currently having the issue occur. 

@commanderclif  Hi, no we empty trash immediately, draft and archive sent-items to 6 months. I do think MSFT changed something and Apple is unaware since it's on a Catalina and Big Sur laptop; I don't think Apple change their client.  I tried to open a case with MSFT and they started telling me that "you know AppleMail is an Apple product..." basically call Apple. Oh and show me the error message ...we'll "No new mail"  when there is a bunch that's the error message. Sigh. I will call Apple today and they will tell me to call MSFT since it's a MSFT server.  The classic IT Catch-22 or finger-pointing.



Hi, I have the same problem as you have after upgrading to Big Sur. On Catalina the exchange account worked fine.


Someone suggested to open mail holding the option key. Tried that, but that didn't resolve the issue.


Macbook Pro 2020, Big Sur 11.1

I am now having the same issues.  Was working fine since upgrading to Big Sur but only in last 24 hours all incoming email stopped and I have to quit and restart Mail to get new mail to come in and even then it's a one time thing.  I've deleted the Exchange account and have re-added but it's not synching past 1,072 emails....and there's 70K emails in the inbox.  Though large number, never been an issue before.  I hate Outlook but am now trying to see if that works.  Mail has been the best mail client I feel I've used and discouraged to keep having issues come back as this is not the first time.  Will monitor here to see if any solutions come up.  But for now, going to see if synching over the weekend helps while I use the crappy Outlook.

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best response confirmed by commanderclif (Copper 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.

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