I eventually caved in a couple of years ago and migrated our corp email system to MS (I'm the MD and we are a precious metal "partner"). Our MX records go to m

I eventually caved in a couple of years ago and migrated our corp email system to MS (I'm the MD and we are a precious metal "partner"). Our MX records go to my trusty Exim n rspamd MTA on prem. If MS take the piss with subscription costs then, I'll simply move us elsewhere. If they all take the piss, I'll expand our Dovecot somewhat and worry about a calendaring app. I've been doing email systems for about 30 years now and I think I have a handle on some of the issues involved.