Scanning User Mailboxes for Spam and Training the Bayes Filter

The script below requires a mail transfer agent such as Dovcot that is set up to place mailboxes under the user's home directories in /home. Upon referencing this script from crontab, it will periodically scan all user mailboxes for the Junk folder and then automatically train the Spamassassin bayes filter.

sa-learn-junk-folders.sh

#!/bin/sh
###########################################################################
##  Copyright (C) Wizardry and Steamworks 2017 - License: GNU GPLv3      ##
###########################################################################
# A script to make amavis / spamassassin learn spam mail through bayes    #
# from all the mailboxes present on the system.                           #
#                                                                         #
# For this script to work, a mail-server must be configured by enabling   #
# IMAP mailboxes stored in the user's home directory, users should have a #
# virtual mailbox "Junk" created into which they can place spam E-Mails.  #
# After that, you can configure the script and reference it in crontab.   #
###########################################################################
 
###########################################################################
#                             CONFIGURATION                               #
###########################################################################
 
# The name of the Junk folder - under Dovecot, this is commonly "Junk"
JUNK_FOLDER="Junk"
# The path to the spamassassin database.
SPAMASSASSIN_DATABASE="/var/lib/amavis/.spamassassin"
# The mailbox type can be either: Maildir, mail or sdbox
MAILBOX_TYPE="sdbox"
 
###########################################################################
#                                INTERNALS                                #
###########################################################################
 
# Train spam from junk folder.
for i in `find /home/*/$MAILBOX_TYPE/ -type d -name "$JUNK_FOLDER"`; do
    HOME_FOLDER=`echo $i | awk -F"/" '{ print $3 }'`
    sa-learn --use-ignores \
        --dbpath "$SPAMASSASSIN_DATABASE" \
        -p "/home/$HOME_FOLDER/.spamassassin/user_prefs" \
        --spam "$i" > /dev/null 2>&1
done
 
# Sync databases
sa-learn --dbpath "$SPAMASSASSIN_DATABASE" --sync > /dev/null 2>&1