Mailscanner is an e-mail security and anti-spam solution for e-mail gateways. In combination of postfix it uses a very ugly way messing around in postfixs queue directories. Anyways .. if you are still interested, keep reading.
Mailscanner was removed from Debian, so it's not available in wheezy. Anyways ... there is a web 2.0 Frontend for Mailscanner, called Baruwa, which provides mailscanner packages for Debian.
Add the baruwa sources file
cat > /etc/apt/sources.list.d/mailscanner.list << 'EOF'
deb http://apt.baruwa.org/debian wheezy main
deb-src http://apt.baruwa.org/debian wheezy main
EOF
Optional, install the GPG key for the repository
wget -O - http://apt.baruwa.org/baruwa-apt-keys.gpg | apt-key add -
If you're running squeeze with Mailscanner, you should do this before upgrading to wheezy. If you are installing Mailscanner on a fresh wheezy, just:
aptitude update && aptitude install mailscanner
As of Version 4.78 and above, you can place you local changes into /etc/MailScanner/conf.d/, no need to mess directly around into /etc/MailScanner/MailScanner.conf