Update:

Looks like Emails to Microsoft providers are working again!

------------------------------


Sadly, Hotmail/Outlook has classified our server as Spam and we cannot seem to resolve this since they do not provide any useful information. I reviewed if spam was actually sent out and I suspect some users simply flagged too many mails sent from us as spam/junk mail. We do not really send out a lot of mails so I suspect this came from users that had notification settings set up that alert them of new posts on some threads in our forums via e-mail.