To be honest, such an approach to spam filtering through headers and email addresses is not efficient or the best way to handle things. Is there any way for people to set up a "rules" file for their mail server so we can have our mail server scan the mail directly itself by sender, From, subject, and body? This is the way all the hosts I've worked with now do things, and it is much more effective and has better finite control. White listing and black listing takes too much time to manage, and this approach produces an endless list that isn't useful, as most spammers now use software that can fake email addresses and headers. As an example of what I mean, here is one set of rules lines from my old rules file at another host.
B~(\w|-)*(house|days|concepts)\.(com|net|org|biz|info|us|ru):NUL
F~(\w)*coo.net:NUL
Note the first rule looks in the "B"ody of the email to find any non-space inclusive string that begins with any letter/number character or a dash, followed by any substring in the second "( )" in an OR structure, followed by a "." and then an domain suffix in subsequent "( )" OR set. Many spammers are trying to get you to click through to an aflliates program, so I simply sceen for that domain in then body, send it to NUL email acount(Deleting IT), and it doesn't matter where or who it came from.
The second line accomplishes a similar pattern as to a Black list by deleting mail with any address coming from coo.net.
"AND" and "OR" conjunctions can also be used to do more complex fitlering based on mulitiple fields, plus in place of NUL one can indicate a specific email address under the domain as a spam catch account if you'r concerned about being able to review all spam before deleting it. Since this approach works by server and domain and is infinitely refinable, there is no need to turn spam filtering on and off for a domain or individual accounts.
Similarly, I can also screen for a blank body, or blank body and subject, for embedding of java or activex objects used for invasion and trojan techniques used in HTML mail.
A rules file usually is placed inside the root of user's account, typically as "rules.ima" or something, and the mail server loads it for the default domain as a whole.
This is a much more powerful way to go, and it is implementable on Win servers, and hence there would be no need for an plugin system like SpamAssasin.