Confirmation Mail is not Working

When an user sign ups in my site then a mail is sent to me describing the following:

The original message was received at Wed, 6 Jan 2010 19:44:59 -0700
from localhost [127.0.0.1]

----- The following addresses had permanent fatal errors -----
<xxxxxxxxxxx@yahoo.com>
(reason: 553 sorry, your mail was administratively denied. (#5.7.1))

----- Transcript of session follows -----
... while talking to relay-hosting.secureserver.net.:
>>> MAIL From:<xxxxxx@yahoo.com> SIZE=1271
<<< 553 sorry, your mail was administratively denied. (#5.7.1)
501 5.6.0 Data format error

Afet this message it shows a good looking mail which should be sent to the user who signed up. But It comes to me. Otherwise when a member click on Forgot Password to retrieve his Password then The mail comes to my (admin's) address than to his email address.

What is the problem with sending mail to appropriate user?

Thanks a Million in advance.....

Expecting a solution or suggestion .....

Are you using godaddy for hosting by any chance?

If so, this is a common issue on godaddy.

The email addresses you set dolphin up to use must match your domain name. If they don't that error is the result.

Anyhow. Not a dolphin issue. It's a hosting mail server issue.

Aaaaah .... Thanx man.... It worked!!!!