Turn off SMTP by domain

[ssiAdmin]

Is there a way (maybe through Virtuozzo firewall) to turn off smtp on an individual domain basis.

I'm trying to get to the bottom of a spam issue. I have the server set to authenticate. I've read most of the posts here in the forums. Looking for quick fix while I implement something more long term. I need to get off a black list and I can't do that until we stop the outgoing spam.

Thanks in advance,
Art