I can't tell you why cpanel does not incorporate MailScanner into their installation like they do with exim. but, I can tell you that it works greate on my servers.
If you don't like it, or it is giving your server a hard time with email, than you can unstall it with ease.
I haven't found MailScanner to be cpu sensitive yet.
cpanel has their own recommended config settings that fit well into exim "one of the reasons I chose cpanel install over every one else" In fact I had to un-install my last MailScanner installation on one server that was recommended in another post "lot of work".
cpanel installation of MailScanner comes with ClamAV and does what you want it to do.
P.S. I'm personally much more interested at present in introducing anti-virus software on my server (that strips off the virus but still delivers the message with appropriate advisories of what has been done) than the much more controversial policy of attempting spam control on behalf of my clients.
Here is the basic setup I used if you want to try it out.
NOTE: My servers all have RedHat 7.3 to 9.0, If the installation is different for other OS than any ones input is more than welcome.
Code:
wget http://layer1.cpanel.net/mailscanner-autoinstall-1.5.tar.gz
Code:
tar -zxvf mailscanner-autoinstall-1.5.tar.gz
Code:
cd mailscanner-autoinstall-1.5
"After you install, You can setup your config."
Code:
edit /usr/mailscanner/etc/MailScanner.conf
"When you are done you need to resart MailScanner"
Code:
killall -9 MailScanner
Code:
/usr/mailscanner/bin/check_mailscanner
If you have any problems and nothing seems to work to your advantage than you can un-install
Code:
cd mailscanner-autoinstall-1.5