Getting people off my SPAM list

I am running Spam assassin under 10.4.8 server and all is running well. Unfortunately, one of our suppliers keeps sending mails with atachments and no oher text. As such, he's been picked up by SA and blocked. I can go into the SPAM mail box and fish his mails out, but i wanted to get him or his domain put onto some sort of o.k. list. I've tried to learn all of his emails into the notjunkmail system, but he still gets blocked. Any ideas how I can permanently make him an o.k. domain or mail sender?