Unfortunately, Spam Assassin is a global account setting. The only thing Spam Assassin does is label emails with *** SPAM *** in order for your to filter them. If you are missing emails you will want to disable Spam Box and disable auto delete. We do not recommend using Spam Box, Box Trapper, or Auto delete as they can cause your good emails to be deleted.
Thanks, James. That's just what I needed to know. Sadly, we've been getting SO much spam (probably due to our contacts' email accounts being hacked) that it's become a nightmare. I did enable Spam Assassin as you recommended, and it seems to be working just fine. Good to have the "white list" and "black list" options as well.
I'm sorry to hear you are getting a tn of spam like that. It sounds like you have been added to some spammers database. If the spam is not coming from your server but somewhere else, I recommend submitting them to spam cop. You can forward them as well. See the articles below for more info.