Delivery Status Notification (Delay) Post Master

When some of our user e-mail to customers, the mail comes back and the user gets the following message Delivery status notification (delay) Post master.

And the Interscan message security suite monitor is going nuts, on the monitor it display ID 10232 mail not delivered. and not converted.

But i can mail to my gmail account from the work e-mail and it works.

Would a restart work? Need help