Mail is bounced

So here’s the deal. I just pointed a domain to my server, this domain has mail accounts somewhere else, but when I now try to interact with the client, all outgoing mail from my account to his account is rejected.

I am thinking that there must be something checking for his mail account locally on my server because their website is set up here, and not finding anything, just bounces the it.

On a side-note, this has happened twice with different domains each time.

This is the mail system at host

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

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

               The mail system mail for loops back to myself

Did you turn on the “Mail for domain” feature for that site? If so, Postfix will get configured to accept mail for it, no matter what MX nameserver entries might exist elsewhere, and results in a loop when you try to send mail through your server.

Another reason might be when you send mail through your server and have not configured BIND properly with the MX records on that other place.