Have been toying for some time with moving to /e/, which looks really great. What has stopped me so far are the challenges with syncing /e/ with Exchange 365 (How to connect /e/ to Exchange365 server?). Sorry for only chipping in now with my two cents worth, had given up for some time, but am happy that @Manoj pointed me here to this discussion.
Even though this thread started about the email client, some posts included also other components Exchange brings along like calendar and address book, which would be great to include in the native sync as well, because Exchange comes as “package”. For me personally, it’s less about having Exchange emails on my phone. Rather syncing calendar, address book and tasks are essential for me. When testing /e/ on an old phone (/e/ 0.8-20200415…), I can find “Google”, but nothing comparable on Exchange under /e/'s Settings --> Accounts --> add account. Lineage OS has an “Exchange” account option (along google and a few others), which is at least for me a “one-stop-shop” for everything Exchange related. There I can select what to sync (in my case everything but email), which works great even with my employer’s Exchange 365 and its own sign-in infrastructure. I wish something would become part of /e/, as well, as this would be a game changer at least for me. I’d be surprised, if I am the only one in this situation who would like to see an Exchange 365 support beyond emails out of the box on /e/ without much tinkering or intermediaries like NextCloud.
As simple employee, I’m afraid, I don’t have much say in what kind of IT infrastructure my employer uses (Exchange 365, would have voted for FOSS alternatives if anyone had asked me 
) and I think it’s highly unlikely that I can convince them to make money available for helping /e/, as @GaelDuval (and I & possible many more) would like to see…
(BTW, the out-of-the box blocking in /e/ of standard trackers in apps that was mentioned above sounds very interesting!)