We practice giving up on the whole ordeal as we have to send another damn email to Microsoft asking for them to investigate their standards-non-compliant black box email filtering systems which even they don't understand.

Stubborn self hoster reporting for duty

I tried to go the self-hosted route. It became impossible to manage. I don't know how many hours I sunk in to figuring out why, seemingly randomly, my emails were being marked as spam by Google. If you can't get through to Google, you're effectively invisible for most people