Re: local SPAM filtering: was: [Patch] Enable multi-threaded POP3 retrieval

Albrecht Dreß <[email protected]> Sun, 07 Jan 2018 13:44:20 +0100
Newsgroups	gmane.comp.gnome.apps.balsa
Message-ID	<[email protected]>
Hi Jack:

Am 07.01.18 04:11 schrieb(en) Jack:
> Gentoo has quite a large list of apps in their mail-filter category.  I have started to go through them, but so far, the problem for me is that most of the are not suitable for my usage - a single user wanting to filter multiple pop3 feeds.  When I have more time, I'll go through the list with a bit more care than I have bothered with so far.  However, thanks for the suggestions.

I use spamassassin and procmail for local spam filtering.  In short:

(1) install spamassassin, its client (spamc) and procmail

(2) optionally install razor and/or pyzor

(3) initially train the Bayes db with the spam/ham files you can find on the spamassassin site

(4) create a system-wide spamassassin config (Ubuntu/Debian: /etc/spamassassin/local.cf) according to your needs.  I had to add the following for using Pyzor and for better filtering results
---8<----------------------------
required_score 4.0
use_pyzor 1
pyzor_options --homedir /etc/spamassassin
use_bayes 1
bayes_path /var/lib/spamassassin/bayes_db/bayes
---8<----------------------------

(5) for testing, send a RFC822 file (e.g. one message from a maildir mailbox) to spamc: “spamc < message_file”.  The output should contain a new “X-Spam-Status:” header

(6) create/modify the ~/.procmailrc file by adding the following rules at the beginning (stolen from somewhere on the Internet):
---8<----------------------------
:0fw: .spamc.lck
* < 4194304
| spamc

:0:
* ^X-Spam-Status: Yes
Junk/
---8<----------------------------
The first rule sends messages smaller than 4 MByte to spamc.  The second shifts all messages which have been classified as spam to the Maildir mailbox “Junk”.  If you trust your provider's spam headers (I don't; my provider classifies all GPG-encrypted messages as Spam…), you may /prepend/ appropriate rules to shift such messages to Junk, saving the time for the local check.

(7) In the Balsa mailbox configuration, activate “Filter messages through procmail” and set “procmail -f -” as procmail command.

 From time to time, I use the messages in the Junk mailbox to train spamassassin: “sudo sa-learn --spam --progress ~/mail/Junk”.

Hope this helps,
Albrecht.

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