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# Returned email error: unroutable address

* Symptom: Mail to address(es) at a client domain is returned with the following error:
```A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

mailboxname@server.name.here
(generated from user@domain.com)
Unrouteable address
```
*  Cause: Improper setting of the default email address via the control panel.
*  Resolution: Log in to the control panel, select the mail management option, and reset the default email address. For any address other than the master username, the default address must be a full email address in the format username@domain.com.