I'm using Thunderbird on Linux with an Outlook work account. Granted, I have to pay for 'Owl for Exchange' for it work, but I absolutely hate the Outlook program, I'm willing to fork out the $10/yr of my own money just to avoid it.
>>extr0p+(OP)
If you still have IMAP access, thunderbird supports OAuth2 for connecting to O365 IMAP. tbsync for calendar access. Seems to work pretty well currently.