It appears our eMail delivery vendor (Mailgun) has caught the ire of Microsoft's mail servers. (the whole reason we switched to them in the first place).

When you signed up with a Microsoft email we warned you that they often accept mail for delivery and then drop them. Now they're not even accepting them, which is more honest, but still bad. Of course we never send marketing emails.

If you're not receiving emails from us, now you know why!

We have tickets open with the vendor to resolve the issue. They already moved us to another IP, but it got blocked too!