Mail issues MS Exchange in Apple Mail / macOS Big Sur 11.0.1

Found a solution - at least for me - to the Mac Mail App sync issue with Office 365 exchange mail server. Quite the Mail App. From the Finder, "Go" in ~/Library/Mail/V8/MailData. Once there, move out of the folder (I just moved to the Desktop) the file "Envelope Index". Afterward, re-open the Mail App. The file will then automatically re-created. After the end of this re-creation, everything worked fine. It seems to be related (I'm not an expert, though) to the corruption of index files in Local Folders. It may take a while if you have many messages in your Local Folders (more than 16 Million in my case and it took about one hour). Hope this helps

I found that 2 of my devices were setup differently, one was working properly and the other one was not, the only difference was a uncheck box. Check In Mail app, go to Preferences, click on Accounts, then on Server Settings. Unchecked the Automatically manage connection settings.

Hi all,

I see that this continues to be an ongoing issue with no official resolution. There is actually a workaround fix for this.

First, let me start by saying, this isn't an actual issue with Mac Mail. This issue lies within the Exchange protocol used by Microsoft. It seems that there had been a change to the protocol sometime early last year which then causes syncing issues with Mac Mail only.

The workaround fix that I've been using is to go to Accounts and uncheck "Mail" from the problem account. Then add a new account (Using the same email address) but this time click on "Add Other Account." Then select "Mail account."

What we're doing is adding the same account but this time as a IMAP account. Mac Mail will then have the same account signed in twice. This is because IMAP only supports Mail and Notes. The problem account will continue to access your Contact and Calendars.

Now you should be all set. You won't notice any difference in use, you just won't have any more syncing issues.

Hope this helps! I know this has been a pain for many users for close to a year now.

I had the same issue when i first upgraded my MacBook Pro to Big Sur. The way to resolve it is to delete the exchange account from the list of internet accounts in system preference. Then add it back to the list. It then works.

the same issue occurred again later. I just deleted it again, then added again.

I have the same problem with Mojave 10.14.6 and AppleMail Version 12.4.

It is not only a Big Sur problem. In this case the behaviour is not stable. It did not work from Feb. 5 to Feb. 7 it worked from Feb. 7 to Feb. 8 17:xx then it stopped working.

In parallel I use the office365 imap service this works prefectly fine. This seems for me to be an useable workaround using Imap for emails. Calendar synchronization works fine so far.

yep, been having same issue off and on w/ various MacOS, not just BigSur. Something about MS Exchange and Apple Mail that don't mix. It made sense to me to migrate my Exchange/Office 365 acct to MS Outlook. Issues resolved. I know Mac folks love Apple Mail, but there are alternatives.

Try something guys, delete "remove" account and add it again ... I did it and it worked

Thanks this worked for me I just had to put remote.<myworkdomain> into the internal and external URL boxes and all is good now.

I had done this on my iPhone and would have thought those settings would have transferred with the account

Quit and restart Mail holding the Option key. Should load your stubborn Exchange messages. Not a fix, but a faster workaround than rebuilding.

I just gave it (deleting/adding the account) a try and it has resolved my exchange sync problems - for now. Nice.

Im having a nightmare with this issue with one of my clients. Since updating to Big sur their exchange account (via office365) is just not working. If it is removed then re-added it will download everything and seem ok but then just not collect any new mail. I have tried re-adding the account several times and also tried adding the account with manual setup and also as an smtp/imap account - none of which work. After several hours with Microsoft support, their only solution is to use the outlook app - which of course it works in. This is a pretty huge problem and I'm really surprised a bug like this is going without Apple's attention despite there already being several incremental updates since the first post. Anyone else had any success finding a solution?

Just started having issues. My exchange emails don't show in mail until I quit and relaunch the app. Was fine up until a few days ago.

Similar Issue with mac mail on iMac. Microsoft Exchange email will NOT download new messages to Mac Mail desktop program. Some problem before Big Sur, now, with Big Sur, will not download at all, unless computer is restarted or, sometimes, will with program restart. Read somewhere it may be a security patch conflict. Service is through GoDaddy and neither they nor Apple have been able to resolve the issue.

SAME issue on seperate iMac, on seperate network, different ISP, in completely different geolocation.

iMac (Retina 5K, 27-inch, Late 2014), Big Sur OS 11.0.1 (20B50), Mac Mail 14.0

I have issues with exchange too, but slightly different issues. Any incoming mail with an attachment won't be saved properly on my Mac locally. Also the emails in different devices (iPhone, iPad, other MacBook Pros) for the same exchange account won't sync with each other now.

I didn't have such issues before. They occurred after I upgraded to Big Sur.

I called Apple custom service. Their answer is that this is an exchange-Apple issue. They cannot solve it alone.

Similar issue. No resolution. Large single inbox folder, will not sync all messages and new messages not syncing. Only an issue since Big Sur installed.