[exim] block a particular domain.

Hello,

I am new to exim. I want to block all the mails from a particular domain
as the mails from that domain is constantly increasing my mail queue which
is hampering my server performance.

Please advise where should i edit in the config file so that all the mails
from that domain gets deleted instatntly and not increase the mail queue.

Thanks..
Suprateem Das..