Bartłomiej,
> this seems to be one of least documented functions in amavisd-new.
> I cant find any info how to use it, if to use it, and if not,
> then why not to use it. Nothing,
This is mostly because hardly anyone uses it, there are no experiences
with latest versions, and experience with old versions was unsatisfactory.
What little documentation there is, is in release notes.
Like with any new feature, it was first documented there:
amavisd-new-2.5.1 release notes
- dspam options changed with version 3.8.0, replacing option --feature
with --tokenizer; reported by Jim Knuth;
amavisd-new-2.1.0 (amavisd-new-20040815) release notes
- incompatible change: DSPAM 3.0 or better is needed (if $dspam is enabled),
no longer works with 2.x;
- dspam header fields are now inserted into passed mail if all recipients
are local;
amavisd-new-20040701 / amavisd-new-2.0 release notes
- provisional/experimental support for DSPAM spam checker (pre 3.0):
if configuration variable $dspam is nonempty and represents a path to
a 'dspam' program, a message is passed to dspam and its inserted headers
of the form X-DSPAM-* are axtracted and then made available for
SpamAssassin rules to check and score if desired.
All messages are currently presented to dspam as the same user, affecting
how its database is being built. False negatives and false positives
(based on SA assessment) are fed back into DSPAM as a simple form
of auto-learning. Works reasonably well, but do not expect miracles.
See subroutine spam_scan.
Here is how DSPAM can be installed to be able to be used by amavisd-new:
dspam 2.x:
./configure --enable-alternative-bayesian \
--with-userdir=/var/amavis/dspam --enable-signature-headers \
--without-local-delivery-agent --without-quarantine-agent
dspam 3.0.0:
./configure \
--with-dspam-home=/var/amavis/dspam --enable-signature-headers \
--without-delivery-agent --without-quarantine-agent
make install
chmod u-s,a+rx /usr/local/bin/dspam
chown vscan:vscan /var/amavis/dspam
User 'vscan' may need to be added to DSPAM trusted.users file.
The following can be inserted into the SA config file (local.cf)
to make it recognize and incorporate DSPAM's assessment:
header DSPAM_SPAM X-DSPAM-Result =~ /^Spam$/
describe DSPAM_SPAM DSPAM claims it is spam
score DSPAM_SPAM 0.5
header DSPAM_HAM X-DSPAM-Result =~ /^Innocent$/
describe DSPAM_HAM DSPAM claims it is ham
score DSPAM_HAM -0.1
Eventually DSPAM support should be removed from amavisd-new, as soon as
SA will be able to call it on its own.
> I dont really know how it works.
See subroutine check in package Amavis::SpamControl::SpamAssassin,
file 'amavisd'.
It passes a copy of a message to dspam and reads back its resulting message.
All header fields starting with X-DSPAM are extracted from this result,
and inserted into an original message, but only for recipients matching
@local_domains_maps. After extracting these headers the resulting message
from dspam is discarded.
Then, header fields X-DSPAM-Signature and X-DSPAM-Result are inserted
into a copy of a message that is being presented to SpamAssassin
(no real copying takes place, it is just easier to describe it this way).
It is up to SpamAssassin rules (e.g. in local.cf) to make something
out of these header fields, or not.
Last, like Gary said, some autolearning on dspam is attempted,
learning as spam if score is above 7, as spam for score below 0.5
(both limits are hard-wired).
That's about it. I haven't tried it for the last three years.
It is a proof-of-concept code mostly. Someone who has interest
is welcome to improve it.
> And still, I havend found a solution, to leave Dspam signature in
> headers. Anybody with any clues? Mark?
With versions later than 2.1.0, all X-DSPAM-* header fields
are supposed to be copied to a passed message, if recipient is local.
Mark
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