I'm new to cpanel. I'm trying to figure out why my email are getting bounced back. this is a email from one of my clients. I also have many other clients getting the same thing... I'm not sure how to fix this issue. everything seems to be working fine. most email works. but there are a lot of domains it just not working on...

please help


-----Original Message-----
From: Mail Delivery System [mailto:Mailer-Daemon@xxxxxxxx.com]
Sent: Thursday, September 09, 2010 4:09 PM
To:
Subject: Warning: message 1Ot4Bq-0002X5-I4 delayed 48 hours

This message was created automatically by mail delivery software.
A message that you sent has not yet been delivered to one or more of its recipients after more than 48 hours on the queue on hosting1.tux-support.com.

The message identifier is: 1Ot4Bq-0002X5-I4
The subject of the message is: Greetings from xxxxxx!
The date of the message is: Tue, 7 Sep 2010 14:50:58 -0500

The addresses to which the message has not yet been delivered are:

@kenwoodusa.com
@utsci.com

No action is required on your part. Delivery attempts will continue for some time, and this warning may be repeated at intervals if the message remains undelivered. Eventually the mail delivery software will give up, and when that happens, the message will be returned to you.