Proxmox Mail Gateway (PMG) is a great solution for filtering incoming and outgoing mail for spam. By default SpamAssassin in is not trained with what emails should be considered spam and what emails should be allowed to be passed through PMG. As such we need to provide PMG with what is SPAM and what is HAM (not spam). Strangely enough PMG doesn’t provide a very intuitive way to achieve this, so we wrote a script which will feed all junk mail from cPanel accounts to PMG to train SpamAssassin.
Of course tweaking in PMG is also required to make sure you don’t block legitimate mail, but this method certainly gets one started and provides a good base for filtering spam mail.
Step 1 – Create script on PMG to accept data from cPanel server
#!/bin/sh case "$SSH_ORIGINAL_COMMAND" in report) sa-learn --spam ;; revoke) sa-learn --ham ;; *) echo "Invalid command?" ;; esac
chmod +x /bin/remote-commands.sh
Step 2 – Generate SSH key on cPanel
ssh-keygen -t rsa -b 4096
Authorize the generated key on PMG with the following command:
ssh-copy-id -i ~/.ssh/id_rsa.pub root@pmg-ip
Step 3 – Edit authorized_keys on PMG to use restricted command
Add command=”/bin/remote-commands.sh” in front of the ssh key as follows:
command="/bin/remote-commands.sh" ssh-rsa KEY.. root@hostname
Step 4 – Create the spam reporter script on cPanel
#!/bin/bash MAILFILTER=PROXMOX_MAIL_GATEWAY_MAIN_PUBLIC_IP for i in /home/*/mail/*/*/.spam/cur/* /home/*/mail/*/*/.Junk/cur/* /home/*/mail/.spam/cur/* /home/*/mail/.Junk/cur/* /home/*/mail/*/*/.spam/new/* /home/*/mail/*/*/.Junk/new/* /home/*/mail/.spam/new/* /home/*/mail/.Junk/new/*; do if [ -f "$i" ]; then STATUS=`file "$i"` if [[ $STATUS == *"gzip"* ]]; then gunzip -d -c "$i" > /tmp/tempmail.$$ fi if [[ $STATUS == *"bzip2"* ]]; then bzip2 -d -c "$i" > /tmp/tempmail.$$ fi if [[ $STATUS == *"SMTP mail"* ]]; then cp "$i" /tmp/tempmail.$$ fi cat /tmp/tempmail.$$ | ssh -i ~/.ssh/pmg root@$MAILFILTER report if [ $? != 0 ]; then echo "Error running sa-learn. Aborting." exit 1 fi rm -f "$i" rm -f /tmp/tempmail.$$ fi done
Be sure to replace PROXMOX_MAIL_GATEWAY_MAIN_PUBLIC_IP with PMG IP
chmod +x /bin/spam-reporter.sh
Step 5 – Create timer specs and timer on the cPanel server to invoke the feeder
[Unit] Description=This service automatically reports spam. Wants=spam-reporter.timer [Service] Type=oneshot ExecStart=/bin/spam-reporter.sh [Install] WantedBy=multi-user.target
[Unit] Description=This is the timer to check for spam and report it. Requires=spam-reporter.service [Timer] Unit=spam-reporter.service OnCalendar=*:0/5 [Install] WantedBy=timers.target
Step 6 – Enable the timer
systemctl daemon-reload && systemctl enable spam-reporter.timer --now
Each time junk mail is then received on your cPanel server, this will then be fed back to PMG.
Credit for the scripts go to CRC