outgoing spam e-mail


I receive so many bouncing e-mails like this in reply to messages allegedly sent out from accounts that do not even exist. I doubt there might be a virus or spamware in the system or someone is using the server to relay e-mails. I have Postfix 2.6.6 but I’m not sure how to proceed!

Thanks for your help

OS: Centos: 6.5, webmin 1.730

This is the mail system at host mail.xdomain.com.

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.

               The mail system

shredl108@xdomain.com: data format error. Command output: shredl108: Mailbox
does not exist


Hmm, what is the output of this command on your server:

mailq | tail -1

That will show if there are messages in your mail queue, and if so, how many.


The output : Mail queue is empty
Yet, Can I somehow stop all outgoing mail until I find the problem?

In header e-mail message find:

"Return-Path: <“your@real-email.com>”

in mail header : Return-Path: <>
what does that mean?