Multiple Recipient Whitelist & Blacklist Rules

[Jeff Ellis]

I have two users user1 at example.com and user2 at example.com that both
receive email from someotheruser at otherexample.com.

user1 wants all email from someotheruser blacklisted but user2 wants
email from someotheruser whitelisted.

i have set up spam.whitelist.rules and spam.blacklist.rules as follows:

/etc/MailScanner/rules/spam.whitelist.rules
From: someotheruser at otherexample.com and To: user2 at example.com  yes
...
FromOrTo:    default    no

/etc/MailScanner/rules/spamblacklist.rules
From: someotheruser at otherexample.com and To: user1 at example.com  yes
...
FromOrTo:   default   no

If email comes in from someotheruser to either recipient alone, the
rules work as expected but if the email has both recipients in the To:
line (or if it's BCC'd to both) the email is whitelisted and user1
receives email she doesn't want. MailScanner.conf is seeing the rulesets
correctly since it works if either user is the only recipient. I know
this can be done by setting up another Postfix server that splits out
the recipients and relays on to the main Postfix and MailScanner server
but wondered if it can be accomplished just through MailScanner?

CentOS 4.3
Postfix 2.2.11
MailScanner 4.56.6-1

Thanks for any help with this.