I have an outlook.com account. The primary alias is at a domain that I own, and I have an @outlook.com alias associated with it. When I try to send an email to the alias, I get an error that the mailbox is not available (error below). It also does not look like I can send from the alias either.

This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

        *** Email address is removed for privacy ***




Final-Recipient: rfc822;xxxxxxxxxx@outlook.com
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;550 Requested action not taken: mailbox unavailable (-908265849:3844:-2147467259)