Incoming email not being recieved

Incoming mail isn't being recieved. I ran a test email and it came back as
Sorry, we were unable to deliver your message to the following address.

< cs@appledatabase.com>:
Remote host said:
550 5.1.1 < cs@appledatabase.com> Recipient not found. < http://x.co/irbounce>
[RCPT_TO]