How To Easily Censor External Web Email Sites in Firewall

I found a super-simple way to block access to external email providers like GMail or HotMail or Yahoo Mail in firewall. The process while trivial to configure has a caveat.

Why:
External web emails are a potential source of virus and malware which can infiltrate the corporate network.

How To:
Block all URL’s containing the word mail. In my experience all web email systems invariably has the word mail somewhere in their URL string. This is very simple to configure in Agnitum Outpost Firewall. Enable Site Blocking and in the list of sites add the word mail.

Caveat:
It may block few legitimate sites and/or blog posts containing the word mail like www.theglobeandmail.com