11th Systems Administration Conference (LISA '97)
Selectively Rejecting SPAM Using Sendmail
With the growing popularity of the Internet, unsolicited
electronic mail (spam) has become a major concern. It fills up user's
mailboxes, clogs mail relays, wastes postmaster time, and creates ill
will for sites that have been used as a relay. Most sites want to
filter spam before they receive it but filtering spam is hard to do
without filtering legitimate mail messages.
This paper discusses
what characterizes spam and describes rulesets that can be added to a
sendmail version 8.8  sendmail.cf file to selectively
reject mail from specific addresses, domains or IP addresses and to
prevent spammers from relaying mail through a site. It discusses the
different issues facing corporate sites and the special issues facing
Internet Service Providers (ISP). The rulesets presented have been
implemented as M4 template files so they can be easily
integrated into a sendmail 8.8 sendmail.cf file as a FEATURE using M4.
These rulesets are currently in use at Harker Systems and other sites,
and are available via anonymous ftp.
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