All mails sent by the website do not end up at microsoft email boxes at the moment.
That includes notification mails for new PMs, notifications for new posts in subscribed topics, etc etc.
First evidence provided by MS shows too many recipients have reported our mails as spam/junk.
I've asked for specific email information, because AFAIK, all our mails include a link to unsubscribe.
Needless to say, it's extremely frustrating