I only occasionally had problems with outlook.com, I contacted them, their spam system is an outsourced blackbox. They advised me not to send mass emails... Which I don't of course. Gmail and Apple never gave me any problems. Yahoo banned me after my first mail, no idea why but it seems to work now. I feel like I'm fighting the good fight (decentralize all the things!) so I'll just accept the shortcomings, which are in general, not that many. There are even some nice things like I can have mail addresses that go to both me and my wife, unlimited spam addresses etc.