9th March 2017, 9:36
Just thought I'd give some real-life track record with a not so standard setup. Since KDE-PIM is basically not usable for Exchange accounts (not even via Davmail unfortunately, since the compositor is not compatible with Outlook generated HTML) and Thunderbird, even though it has workarounds and tries to support all features, some of them work a bit flaky, thus I thought I'd try installing Gnome's Evolution in Maui. After installing tons of dependent packages and the evolution-ews connector, I've created an Office365 EWS Exchange account and played some time with it. A short summary is that EVERYTHING WORKS! 
It is quite unbelievable, but the ews connector supports 100% of Exchange functionalities I use (even configuration of Out of office messages, free/busy querying of other users when creating new meetings and setting Important flags). And it is VERY fast, much faster than Thunderbird via IMAP. Moreover, Thunderbird cannot connect to Exchange servers that disable IMAP access (only via Davmail, which is quite slow). So I have to conclude that my experiment was 100% successful and I will keep on using Evolution (and hope I don't find some showstopper )
It is quite unbelievable, but the ews connector supports 100% of Exchange functionalities I use (even configuration of Out of office messages, free/busy querying of other users when creating new meetings and setting Important flags). And it is VERY fast, much faster than Thunderbird via IMAP. Moreover, Thunderbird cannot connect to Exchange servers that disable IMAP access (only via Davmail, which is quite slow). So I have to conclude that my experiment was 100% successful and I will keep on using Evolution (and hope I don't find some showstopper )