I have a web server connected to the net via DSL and am using a dynamic dns service. So far everything seems to be working fine, I can send and recieve mail no problem. I would like to prevent certain accounts from receiving mail from anywhere but localhost. Gotta be easy I just haven't been able to find the answer.

I'm running slackware 9.0 and have upgraded sendmail to the latest version via swaret. Any help would be appreciated.