Let's clear up some confusion. I think I misunderstood when you wrote the following.
Exchange mail from Outlook in my Apple mail
You are not using Outlook.app but Mail.app to connect to your Exchange account. Both apps can connect to multiple types of email accounts. Exchange, IMAP and POP. What the window users in your company use to get Exchange has nothing to what you use on your Mac. What matters is the version of Exchange server.
Apple Mail can connect to Exchange as long as it meets one of these requirements.
Requires Microsoft Office 365, Exchange 2016, Exchange 2013, or Exchange Server 2010 (SP2 or higher).
Try this to fix your Exchange account.
Remove the Exchange account in Mail > Preferences > Accounts.
This takes you to System Preferences > Internet Accounts.
Uncheck to remove the account. Not just uncheck Mail for Exchange.
In your User's Library/Mail folder....
- Verify the Exchange data was removed when you removed the account.
- Go to your User's Library > Mail > V5
- You'll see alphanumeric folders, look inside. If you see the Outbox, this is the local "On My Mac" folders.
- We don't want to find a folder for Exchange. Check to verify that is was removed. If you find the folder, then with Mail quit, delete the alphanumeric folder containing your Exchange data.
Clutter is a default Exchange folder, Exchange also has it's own Outbox. This shows Exchange account (the alphanumeric numbers are unique). You might also see custom folders you have created.
Next.... in V5 you should see a MailData folder. Delete any files with Envelope in the name.
Back in System Preferences > Internet Accounts
- Add your Exchange account back.
- Open Mail, It will reindex your messages.
- Exchange will download again from the server.
My advice: When a new version of macOS is released DO NOT upgrade until it has matured. Unless there is some urgent need to upgrade then wait until the final version (.5 or .6) is released to upgrade. Lastly, check here in Apple Discussions to see if Exchange users are having any issues.
