spfmilter - SPF mail filter module

Sendmail includes a facility for plugging in custom mail filters,
called milters.  It's documented here: http://www.milter.org/milter_api/
Spfmilter implements the Sender Policy Framework (http://spf.pobox.com/)
as a milter, using the libspf2 library.

The idea of SPF is to prevent email forgery.  Each participating
site sets up a little definition of which hosts are allowed to send
mail claiming to be from that site.  When another site receives
mail, it checks the permitted-senders definition for the originating
site.  If the check fails, the mail is rejected.

Setting up the permitted-senders definition is very easy, you go
to the SPF Wizard at http://spf.pobox.com/wizard.html and fill out
a little form, then put the resulting string into your DNS records.
This milter implements the second half of SPF, checking the mail
you receive against other sites' SPF records.

See the manual entry for more details.

Feedback is welcome - send bug reports, enhancements, checks, money
orders, etc. to the addresses below.

    Jef Poskanzer  jef@mail.acme.com  http://www.acme.com/jef/