Thanks for replying..
Actually the problem is that the customer is getting these kind of mails in some numbers.
From: <
Mailer-Daemon@domain.com> (Mail Delivery System)
To:
mail-admin@domain.com
Date: xxx, xxxxxxx 01:11:36 +0530
Subject: Undelivered Mail Returned to Sender
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to <postmaster>
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
Why these kind of mails are coming and can we stop these from originating through brightmail.
Is there any problem with the brightmail r with the internal mail server r what can be the issue