I host my own email stuff too (private stuff and for a couple of friends) and sending to microsoft domains (hotmail, outlook.com) consistently gives me the most problems. Right now it seems to be ok again but I always make sure that people using my domains are fully aware of all these problems.

Edit: not long ago I used a gmail account to contact microsoft support to get them to remove me from their blacklist again (couldn't use my normal email for obvious reasons). Ironically enough their reply got marked as spam by gmail (something in my included message parts might very well have triggered that but I had to laugh out loud at the situation).