I sent this email to the Rehdat list, but I thought the Centos users might be more inclined to have the command-line solution I am looking for, so I thought I would post it here too: I would like to add anti-virus to my email server. Currently I have Postfix, Dovecot, PHP, and Squirrelmail installed. The users only use Squirrelmail to access mail. I am looking for command-line instructions, since I have limited access to the server itself (I am using SSH). ClamAV seems to be most common linux AV package, so I assume I should be using that. I'm not sure if I should be using Amavisd or MailScanner, or neither. I believe I need one of them to act as the glue that connects Postfix to ClamAV. Apparently none of these packages (Amavisd/MailScanner/ClamAV) are part of RHEL5, so I have to get the RPMS from somewhere else. Is there some standard way of adding AV to Postfix?