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+Title: Filtering spam mails with bogofilter
+Date: 2020-03-22
+Lang: en
+
+I'm running a [Postfix](http://www.postfix.org/) server here at home to process incoming mail. To integrate spam filtering I'm delivering mails via [procmail](https://en.wikipedia.org/wiki/Procmail) - it's as simple as setting `mailbox_command = /usr/bin/procmail` in postfix' `main.cf`.
+
+Spam filtering works by invoking the filter ([bogofilter](https://bogofilter.sourceforge.io/) in my case) from procmail like this:
+
+	:::shell
+	:0 fw
+	| /usr/bin/bogofilter -uep
+
+This command will pipe the mail content through bogofilter which will add a `X-Bogosity` header denoting the spam status of the mail. 
+
+A second procmail rule moves all spam to a designated spam folder on my IMAP server:
+
+	:::shell
+	:0
+	* ^X-Bogosity: Spam.*
+	$HOME/.maildir/.INBOX.Spam/
+
+For training I use two designated folders on my IMAP server: *LearnSpam* and *LearnGood*. I'm simply moving mails that I want to train as spam to the *LearnSpam* folder. Once per hour I train spam/good mails using this script:
+
+	:::shell
+	#!/bin/bash
+	SPAM_FOLDER=$HOME/.maildir/.INBOX.Spam.LearnSpam
+	if [[ -d $SPAM_FOLDER ]]; then
+	        SPAM_CUR=$SPAM_FOLDER/cur
+	        # only invoke bogofilter if there are mails in the folder
+	        if [[ "$(ls -A $SPAM_CUR)" ]]; then
+	                /usr/bin/bogofilter -s -B $SPAM_FOLDER && rm $SPAM_CUR/*
+	        fi
+	fi
+	HAM_FOLDER=$HOME/.maildir/.INBOX.Spam.LearnGood
+	if [[ -d $HAM_FOLDER ]]; then
+	        HAM_CUR=$HAM_FOLDER/cur
+	        # only invoke bogofilter if there are mails in the folder
+	        if [[ "$(ls -A $HAM_CUR)" ]]; then
+	                /usr/bin/bogofilter -n -B $HAM_FOLDER && rm $HAM_CUR/*
+	        fi
+	fi
+
+The script is invoked via cron.
+