Milters or SpamAssassin plugings

Matthew Seaman m.seaman at
Sat Apr 12 06:09:43 UTC 2008

Robert Davison wrote:
> I'm running the base Sendmail with Mailscanner and SpamAssassin from
> the ports.
> A simple question....
> I'm installing SPF to help the fight against spam.
> Which is the most efficient way of doing it.....Sendmail milter or
> the p5-Mail SpamAssassin plug-in. They both do the same, but is one a
> better way than the other ?

Ah -- actually there is a crucial difference in the way SpamAssassin
and milter-spf work.  SpamAssassin uses the SPF status of a message
to add to the spam score it calculates -- typically, a message which
passes all the SPF checks has an approximately zero result on Spam
scoring, as will a message where there is no SPF stuff available at all;
but one which fails the SPF tests will get about 3 spam points. (Which
means that even a message failing SPF checks can be passed as ham)

milter-spf however operates in a binary fashion -- anything that fails
is rejected, anything that passes is accepted.

In general I prefer the SpamAssassin behaviour -- not all the world has
immediately accepted SPF as a good tool against spam; there are any number
of edge cases where a legitimate message can contradict what the SPF
settings say (mail forwarding is a particular problem) and one of the
groups that has adopted SPF most wholeheartedly are in fact, the Spammers

SpamAssassin processing is however much heavier on system resources than



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP:     Ramsgate
                                                  Kent, CT11 9PW

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