In addition to SMTP traffic, 
IMSVA can scan POP3 messages at the gateway as
               clients in your network retrieve them. Even if your company does not use POP3 messages,
               your employees might access their personal POP3 email accounts using email clients
               on
               their computers. 
Gmail® or 
Yahoo!® accounts
               are some examples of POP3 email accounts. This can create points of vulnerability
               on
               your network if the messages from those accounts are not scanned.