Subject: Delivery Status Notification (Failure)
From: "Mail Delivery Subsystem" <[email-masked]>
To: <[email-masked]>
Date: Fri, 07 Apr 2017 16:25:18 -0700 (PDT)

** Address not found **

Your message wasn't delivered to [email-masked] because the address couldn't be found. Check for typos or unnecessary spaces and try again.

The response from the remote server was:
550 5.1.1 <[email-masked]>: Recipient address rejected: User unknown in virtual alias tabl