how to stop mail server for a domain

I run a dedicated server running sendmail/exim mail server. I wonder
if anyone can tell me how to stop mail for one of the domains on the
server. I do not want to disable to whole account only mail. I can't
seem to find anything in the documentation, but that might be because i
didn't look hard enough.

If anyone will be able to tell me how to get this accomplished that
would be great.

Thank you

G.