SPAM on only one domain

[subtype]

I have SpamAssassin and some scripts I found on these forums running on my CentOS server and it is very effectively stopping spam on all but one domain. I have systematically gone through and made 100% sure that all of the settings for the spam assassin are exactly the same on that domain as with the others. I still get over 300 spam emails a day, per email account on that domain, what can I be doing wrong? The Spam Filter is set to on for the email accounts under that domain, and it has the same thresholds and everything as my other domains. Do I need to somehow inform SA that this domain exists?