SMTP Server

Problem Details :
In the application there is a functionality to send mail. Whenever we send mail to internal users who has email id in the company name the email works. The email is not being sent for external users (outside our company's email id).
If you send mail to your username@yahoo.com or username@gmail.com. Is it that in the SMTP server it can be restricted.

Environment: Coldfusion 4.5
DB SQL Server 2000.

Please find below the sample mailer demon failure noticed received.


Can any please help me.

Thanks in advance,
Regards,
Satheesh
----- The following addresses had permanent delivery errors -----
<email@gmail.com>


Final-Recipient: RFC822; email@gmail.com
Action: failed
Status: 5.0.0
Remote-MTA: DNS; asdf.test.com
Diagnostic-Code: SMTP; 550 <test@gmail.com>... Not permitted
Last-Attempt-Date: Wed, 23 Jul 2008 06:56:28


---------- Forwarded message ----------
From: test@gmail.com
To: test@gmail.com
Date: Wed, 23 Jul 2008 14:51:55
Subject: Test