There is some great news for those of you who use 2 Factor Authentication with Microsoft Exchange and Microsoft Exchange in Office 365 and have upgraded to MacOS Mojave. Mac Mail now supports it!
Up until Mojave, if you used 2FA with Microsoft Exchange, Mail did not support the mechanisms that Microsoft uses as part of the authentication process. Most users (me included) would simply get an error and it would never authenticate your account. With Mail in Mojave, Apple has included support for the Microsoft authentication requirements and it works.
Once you have upgraded your Mac to MacOS Mojave, you can go into the Mail app and add your Exchange account. It worked flawlessly for me in the setting up of my corporate account and started syncing email immediately.
As you would expect, Calendar also supports this too. In my case, I had to authenticate my account again in Calendar but once I did, it started the sync process.
The knock-on impact of this is huge obviously as now the Calendar widget will display all of your calendar events in the Notification Center and you get more native notifications from Mail than you do with Outlook for Mac. Plus, you can minimize your time in Microsoft Outlook… which is still not my most favorite app ever.