External mail server for a specific domain, howto?

[pgentoo]

Hi,

I have a few clients that choose to host their domains with me, but run their mail via an in-house or hosted Exchange servers. I have their mail. subdomain pointing to the IP of their Exchange server, and have mail.theirdomain.com set as the only MX entry.

Sending external mail works fine, as it looks up the MX record, and sends the mail straight to the Exchange server.

However, sending mail to them from my server (mostly done via a contact form on the site), or from me directly, fails reporting "user@domain.com : user unknown".

I'm assuming that this domain needs to be not listed in postfix's relay domains list (/etc/postfix/ispcp/domains ?), but that file says not to edit manually, so I'm assuming it will not save my edits.

Is there a way to completely turn off mail for a specific domain in this case, and have the changes persist?

Thanks,
pGentoo

[rbtux]

well is discussed in the forum many times...

you have to edit the files under /etc/postfix/ispcp and /etc/ispcp... this way your changes are not overwritten...