documentation for ClamAV[http://www.rfc-editor.org—A repository of Requests for Comments (RFCs),](http://www.rfc-editor.org—A repository of Requests for Comments (RFCs),)
which define the technical “rules” of modern computer usage
[http://www.procmail.org—The Procmail home page](http://www.procmail.org—The Procmail home page)
Sendmail by Brian Costales, Claus Assmann, George Jansen, and
Gregory Neil Shapiro—The de facto standard guide for everything
Sendmail, loaded with more than 1,000 pages, which gives you an idea
of how complicated Sendmail really is
Postfix by Richard Blum—An excellent book that covers the Postfix
MTA
Postfix: The Definitive Guide by Kyle D. Dent—Another excellent
resource for Postfix
Running Qmail by Richard Blum—Similar to the Postfix book by
Blum except that it covers the Qmail MTA