Failure delivery when reply to a post

[Anakreon Mendis]

When I send a new message to newsgroup it works fine
but when I try to reply to a message, the reply fails
to be delivered.

This is the replay of the mail server after I sent a reply
to a message:
To: anakreon@mathind.csd.auth.gr
Subject: Mail delivery failed: returning message to sender
Date: Tue, 02 May 2006 17:21:39 +0300

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:

  user@symfony-project.com
    Mailing to remote domains not supported

------ This is a copy of the message, including all the headers. ------

Return-path: <anakreon@mathind.csd.auth.gr>
Received: from anakreon by mathind.csd.auth.gr with local (Exim 4.61)
        (envelope-from <anakreon@mathind.csd.auth.gr>)
        id 1Favkx-0002g0-C7
        for user@symfony-project.com; Tue, 02 May 2006 17:21:39 +0300
Sender: anakreon@mathind.csd.auth.gr
To: user@symfony-project.com

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