Stop/block relaying e-mails to a specific address

I have Sendmail configured as my Mail Server on a Red Hat Linux box. I want to block my users from sending e-mails to a specific domain or address. How would I go about this?

thanks

[wizbones]

All your sendmail questions can be answered at http://www.sendmail.org and more than likely you'll find a more specific answer at RedHat.

Course you probably knew that already and just wanted a quick fix right? But I didn't give you one  :P

If'n you don't figure it out repost and I'll dig it up for ya. I myself use Postfix it's much easier to config.

anybody know how to block specific email under any users