I was receiving these errors:
This is the mail system at host codyswartz.us.
I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<firstname.lastname@example.org>: unknown user: “test5”
Final-Recipient: rfc822; email@example.com
Diagnostic-Code: X-Postfix; unknown user: “test5”