[ Thanks to LogError for this link.
]
“With all the spam and viruses circulating the Internet these
days, any network admin worth his or her salt will have appropriate
filters in place to prevent these irritants from getting to users
and customers. My predecessor, unfortunately, was worth far less
than that, so my first task upon assuming the role of a systems
administrator for a small ISP was to establish a mail filter.“With no previous experience with a mail filtering system, I dug
in and started my research. After reviewing open source solutions
such as AmaViS and MailScanner and commercial solutions such as
Postini and Mail Warden, I settled on Exim with the Exiscan-ACL
plugin…”