[jeroenhd]

With excessive spam scores, Microsoft silently ignores your email. Just swallows it up, reports it as delivered, but never actually does, not even in your spam folder.

It's possible that this is a technical issue or a submission server issue, but it's not uncommon for Outlook to make email disappear.

[joaopbnogueira]

This sounds like what's happening to us, but only if the dreaded 25friday.com keyword is included on the email content