Currently Being ModeratedFeb 2, 2013 12:11 PM (in response to lliissaa)
If you are using Mail as client, bring up the bounced message then select View > Message >Raw Source. A window will pop up containing the message as it came in, raw text - no interpretation. If that doesn't clue you to what's wrong, copy/paste the HEADER back here for further diagnosis.
Thunderbird/Outlook/Eudora all have similar means of displaying the raw message.
Currently Being ModeratedFeb 2, 2013 1:21 PM (in response to lliissaa)
It's a message from the mail server that the recipient's address doesn't exist or isn't accepting mail.