Mailscanner is not used in any of the perfect install how-to's
i'd suggest you have a look at this how to and use this one to start of with a fresh newly installed system .. it'll save you a lot of hassle
After that you could look at this one to secure your server a bit more (but it's not essential):
Trust me, get rid of MailScanner, i remember i've worked with it 5 years ago and sucked donkey balls. i use amavisd for scanning my mails for virus/spam.