Mac Mail not Syncing with Exchange email server on MacOS devices

Another update. This morning, my Exchange calendar events in Mac Calendar were unresponsive, so I quit calendar. It then restarted on its own and worked fine. So, I fired up Mac Mail, and boom. It synched with Exchange mail. The only things that I did yesterday as an attempted fix were to (1) delete the saved state files in Mail's Application Saved State folder and (2) turn off VPN. They seem to be coincidental. When Mac Calendar restarted on its own, it seems like something within the OS rebooted itself, and it had nothing to do with anything I did. As far as deleting the saved state folder, I suppose that could have helped kick start Mail, but if it did, it took a long time and multiple restarts of Mail over the course of 24 hours. As far as VPN, I suppose that could have been part of the issue. At the time Mail synched, VPN was not connected.

I did same. This time I noticed the bottom of the left sidebar had progress info saying downloading x out of xxx messages. I've only used webmail client for years so I didn't realize it takes time to download 18 gigs of mail and attachments.

I think when I first setup I was expecting mail to come in with no delay, but system was busy synching mail folders.

For what it's worth, I've been on the phone with Apple technical support regarding this issue for several weeks. My rep has been extremely courteous and diligent and has spent a lot of time with me trying to resolve the issue, but it appears to be a more complex problem. I've also tried the work-arounds by other posters, including deleting and resetting your exchange account, which only works for a short while before the problem recurs. I am told Apple's engineers are aware of this issue and working on a solution, and that they still don't know if the problem originates at the exchange server or if it's an OS glitch. I will try and update this post when I hear back.

So far, so good. I did delete the entire MailData items for Exchange and needed to move the messages in OWA or Outlook. Slowly but surely my Mac caught up and has been more or less normal for the past few days.

Still no good for me. Having got all folders down to sensible numbers of messages, I removed all of my accounts from internet accounts, deleted the MailData folder from ~/Library/Mail/V7 (and the mailbox holding local items, just for good measure). And, just to be sure, rebooted, cleared the SMC and the PRAM. Added my work Exchange account back... and it synced all the way back up to where it had previously stopped and now won't acknowledge any new email. As before, "Rebuild mailbox" works sometimes as a one-off, but still won't sync.

Maybe this is a Catalina vs Big Sur issue now, that the fix worked for you and not me. Or just something else.

This is unbelievable but true - switch your phone off, and bing, mail arrives on your laptop.

Good spot @tresinnoctem - thanks.

Thanks for the suggestions. I'm having the same problem with my Exchange account not showing mail in the inbox on multiple 10.15.7 devices. I also recently upgraded to iOS 14.1 on a couple of devices, but just started noticing the problem in the last day or so. I tried turning off the iOS devices, removing the mail accounts from them, to no avail. I've tried rebuilding the Exchange accounts on the MacOS devices, and that doesn't fix the problem. I find that if I choose to "Rebuild" the mailbox, the messages I've been missing pop right into the inbox, but messages sent after that action still don't show up. All the emails show up just fine in the iOS Mail application, so something changed or is wrong on the MacOS side of things. Not sure what else to try at this point.

Quick follow-up to my post - I found a 10.13.6 machine, configured Mail with my Exchange account, and everything worked fine. I was able to receive messages in my inbox as I would expect. Those messages never show up in the inbox on the 10.15 machine until I rebuild the mailbox. As explained above, this isn't a problem on one particular machine, but all 3 of my 10.15 machines, so I don't see it as being a configuration issue. I need to track down a 10.14 machine, but this makes me think it's a problem with 10.15.7 Mail.

And of of late last night, OX X Mail on my 10.15.7 devices started syncing the inbox normally again, on all 3 of my devices! Other mail clients (Outlook, AirMail) worked fine the entire time. I didn't do anything on the machines before things started working again. At 5pm OS X Mail was still not working, and then when I checked on it 5 hours later, it was working! I was able to send and receive email immediately from my Exchange account, and messages showed up in the inbox as expected. It's still working as of this morning. I have no idea what's going on, but I don't see how it would be a problem on my end (3 different Catalina machines had the problem, 1 High Sierra machine worked fine) and multiple other clients worked just fine (AirMail, Outlook, Outlook through the web). Ughh.

Your post made me think of something. I had over 50k emails in my work email inbox. Occurred to me that's a lot to sync on a regular basis and it takes up 10 gigs of hard disk space. Except for most recent emails I moved all 50k to the "archive" folder. Anxious to see if that fixes my problem.

Just to add to this discussion: I have the sync problem as well, and *I do not have any IOS devices*. I have been using MacMail and Office 365 without incident for some years (since my company decided to disable IMAP off-site :( ) and in the last few weeks it's regularly simply stopped syncing.

For me, reducing the number of emails I have is not an option: yes, I clean up, but I also save a lot - as I need them for later (and as a general point: a fix should not be "change the way you work", it should be "fix the software"!). Others I know have had the same issue, and deleting/remaking the account only worked as temporarily: I'm not in a hurry to fix it.

Of course, part of the problem is Microsoft using a proprietary protocol, but since Outlook is so unbearably horrible, and mind-blowingly stupid (when I open it because Apple mail has stopped, it feels the need to remind me about every meeting in my calendar prior to now that I have not yet been reminded of by Outlook itself), it really is imperative that Apple get this sorted.

Yesterday my Mac Mail stopped syncing with Exchange (Office 365) again, 3rd time in 3 weeks. This time I did delete the account (in System prefs -> internet accts) and recreate it. Interestingly, when the inbox first appeared it was up to date... and then almost immediately it reverted back to its state just before I'd deleted the account (checking ~/Library/Mail/V7 confirmed it had deleted the account folder and made a new one). Very weird. Maybe some state token somewhere getting frozen?

Either way, Apple / Microsoft need to urgently fix this. It's hard to find words to express how bad Outlook is, and my company have disabled IMAP access so my options are limited.

All:

when reading that the Junk folder synced despite the Inbox not doing so, I tried other folders.

The Trash did not so I deleted several thousand emails on both the Mac and the server.

The Trash syncs.

Junk syncs.

Sent syncs.

Drafts syncs.

And, the Inbox syncs when deleting items.

Still, receiving mail does not sync. I am going to try culling the Inbox.

Charles

Having a same problem with 2 different MBPs.

Mail works for a little while after rebooting, but then it stops receiving mail to inbox (or in this case, exchange-folder where all new mail arrive). I can confirm this by comparing iPhone mail and MBP mail. folders.

HOWEVER, f.e. spam-folder is updated normally and keeps.

I'm having same problem with Mail Big Sur 14. It will work for a while, then stop pulling new messages from my work exchange email, then it will work again, then stop again.

I always get mail on my iPhone using iOS mail. I've tried some of the suggestions and they don't permanently solve.

If Apple doesn't fix will have to use Outlook on my Macbook.