Spam filter configurator


  With the growth of the Internet, junk mail has become a problem.  Not
  only do you want to protect your users from receiving junk mail from
  well-known sites, you also need to control who may use your mail
  server to relay mail. Some spammers will try to use your mail server
  as an exploder. You can control this.

  11..  PPrriinncciippllee

  When your mail server receives an email message, there are two
  possibilities. The mail is sent to one of your domains and it is
  accepted, or the mail is not meant for any of your domains and the
  sendmail daemon will try to relay it appropriately to the proper mail
  server.

  There is a third possibility: the message is sent to one of your
  users, but originated from a well-known junk mail sender. You may want
  to delete it right away.


  22..  UUssiinngg nnaammeess oorr IIPP nnuummbbeerrss

  Mail may come from machines which are identified using their host name
  or sometimes using their IP number. It is sometimes more practical to
  classify machines based on their IP number instead of their domain
  name. In the following section you will see that sometimes you are
  allowed to enter a name, sometimes an IP number, and sometimes both.


  22..11..  SSppeecciiffyyiinngg aa nneettwwoorrkk

  You can specify a network number by simply entering the prefix of the
  IP number for that network. For example, for the class C network
  192.168.1.0, you simply enter _1_9_2_._1_6_8_._1_. (note the trailing dot).


  22..22..  SSppeecciiffyyiinngg aa hhoosstt oorr aa ddoommaaiinn

  To specify a host name, you enter the fully qualified name, like
  machine1.domain.com. To specify a domain, simply enter it. This means
  that any machine that is part of this domain will be processed in the
  same way.


  33..  SSeettttiinngg rreejjeecctteedd sseennddeerrss

  You simply enter a list of email addresses, host names, domains and IP
  numbers. All the following possibilities are allowed:


  +o  spammer@junk.domain

  +o  junk.domain

  +o  D.X.Y.Z

  +o  C.X.Y

  +o  B.X

  +o  A

  You must also enter an error message which will be sent back to the
  sender.
  44..  SSeettttiinngg ""rreellaayy eemmaaiill ffrroomm"" bbyy IIPP

  Here, you can enter a list of IP numbers (hosts or networks) for which
  your server will relay mail. You generally enter your various local IP
  networks in this area.


  55..  SSeettttiinngg ""rreellaayy eemmaaiill ffrroomm"" bbyy nnaammee

  Like above, you can enter a list of hostnames and domains for which
  you will relay mail. Generally, you would enter the various domains
  and hostnames on your local network.


  66..  SSeettttiinngg ""rreellaayy eemmaaiill ttoo"" bbyy IIPP oorr nnaammee

  If your server is normally a gateway to deliver mail to other servers,
  you would list those other servers here.