Mass Emails and PM does not work correctly

[Angelus]

Hi.

If I go to ACP-> General Admin->Mass Email and PMs and want to send an email to selected users only I (the admin) get an email.

Than I also get an error email:

[code]This message was created automatically by mail delivery software.  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]

Where Is the problem?

Greetings
Thorsten