bouncing a domain permanently

[Ronny Haryanto]

Hi,

How can I bounce a domain permanently? Ie. I would like to, for
example, refuse to send any mails to [*.]example.com.
Can I use a special token in smtproutes? Something like maybe:

example.com:<error:will not relay there>
.example.com:<error:will not relay there either>

Thanks,

-- 
Ronny Haryanto