Q: Sierra Mail does not sync with my Exchange server anymore.

Works just fine for me on multiple Macs running Sierra. Contact your IT department.

I don't know if this can help but I have the same problem with yahoo and gmail, i.e. no sync done on actions performed on the Mac with macOS Sierra, while everything is synced if actions are done on iOS devices...

Hi David,

Same issue here. I use 2 Exchange accounts, one is syncing without issue, the other only sync on application start. I also recreate the account and rebuild the mailbox; didn't help.

Btw, I don't have anything in connexion logs (Window -> Diagnostic).

I happen to be the Exchange admin of our organisation. I'll look in IIS logs server-side as soon as I can, but I don't think it has something to do with our Exchange servers at all.

FYI, your phone sync Exchange items via EAS (Exchange Active Sync). Mail.app uses EWS (Exchange Web Services). Diferents protocols.

Primarily the Mail app. I also use Outlook 2016 (though less frequently). Both work just fine on multiple machines funning Sierra.

I am facing the same problem and am not able to connect to my EWS Account on Mac. Everything works fine on my mobile devices. Sadly all connection protocols are - even though generated - empty text documents.

After each attempt to connect from my Mac, the in-browser Outlook Web App (OWA) is not working anymore for half an hour stating that there would be an error with my Inbox. When I try to login later everything works again. So there might be some problems regarding security measures. I can't however find any preferences for SSL or the ports used in Mail.

I hope Apple will solve this quickly and thank you for your help.

Dear David,

I am glad it worked out for you. My problem is not primarily with mail as I have figured out that my calendar and contacts have disappeared too. So the problem is with the Exchange Account in general. I did manage to get to the dialog you described, but this did not solve the issue.

I think my problem has to do with ports, as I found one protocol stating that connection has failed on port 0. I double checked all my account information, deleted and re-added the account on mobile (where everything works fine) and there is still this very strange behaviour with the Office Web App (OWA). I receive an error upon login after each attempt to login from my Mac that magically disapperas after half an hour and in-browser Weblogin just works fine again.

Thank you very much for your reply even though it did not work out for me.

Regards,

Clemens

Try testing in a new User and see if you can setup Exchange in the new User.

CREATE A NEW USER

Go to System Preferences --> Create a New User in Users & Groups.

Switch to the New User by logging out/in or use Fast User Switching.

You can skip logging in with an Apple ID unless you need to test iCloud apps. Hit continue then skip.

Only default Apple apps will  be in the Dock in the new User. Go to Applications to open other apps you might want to test.

Do you still see the issue?

    If yes, then the problem is with your base files.

    If no, then the problem is in your User's folder.

Hi there,

I tried connecting to the Server on my Guest Account, which I did not use before and therefore had no Internet/Mail Accounts installed.

The issue still occurs, so my problem is with my base files.

Thank you for your help!

Regards,

Clemens

Hi,

OWA should not be related to your EWS sync issue. It looks like your mailbox may fall in quarantine time to time (already seen this kind of issue). Could you paste the error message you get while connecting via OWA (when you got the issue, obviously) ?

It's possible that Mail now requires the latest version of Exchange. If your server is behind in updates this could be playing a part in your problem.

If you have Microsoft Office, can you test in Outlook?

Hello David,

I have exactly the same issue. Exchange account stop working 5 days after Sierra upgrade.

I've tried a lot if things, and I'm pretty sure now that it has to do with authentication. Connection with exchange server seems to be working fine, but authentication fails.

I've tried with mail, Airmail and Outlook !

I've also tried to revert a backup of mail configuration file from time machine.

I didn't find any working solution.

As somebody already mentioned, your OWA issue is related to authentication failure on mail. After x unsuccessful tries, your account is blocked for a while.

It seems that trying to connect with mail with wrong credential is blocking your exchange account.

If you have any update, I'm really interested. Right now, my only move would be to perform a clean install of sierra ...

Cyril