Judge spam mail and move to the Jank folder.

When the mail is received, it is passed to procmail and can be processed by a custom script.

apt install procmail spamassassin spamc -y

main.cf

vi /etc/postfix/main.cf

virtual_transport = procmail

procmailrc

If it is judged as spam, move to the Junk folder.

vi /etc/procmailrc

SHELL=/bin/bash
PATH=/usr/bin:/bin
DROPPRIVS=yes
USERDIR=/home/vmail/$DOMAIN/$USER
MAILDIR=$USERDIR/Maildir
DEFAULT=$MAILDIR/
LOGFILE=/home/vmail/$DOMAIN/$USER/.procmail.log
#VERBOSE=ON

:0fw: spamassassin.lock
*!^X-Spam-Status.*
| /usr/bin/spamc

:0
*^X-Spam-Status: YES
$MAILDIR/Junk/

Add spam prefix to email subject.

vi /etc/spamassassin/local.cf

rewrite_header Subject *****SPAM*****

master.cf

vi /etc/postfix/master.cf

# Add tail
spamassassin unix -     n       n       -       -       pipe
  flags=R user=spamd argv=/usr/bin/spamc -e /usr/sbin/sendmail -oi -f ${sender} ${recipient}

procmail  unix  -  n  n  -  -  pipe
  flags=R user=vmail argv=/usr/bin/procmail -t -m USER=${user} DOMAIN=${nexthop} /etc/procmailrc

Test for spamassassin

vi /etc/hosts
127.0.0.1 mail.mydomain.com mail.mydomain2.com

echo "XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X" | \
mail -s "test1" -r "ast@mydomain.com" "test2@mydomain.com"

Relearn from the misjudgment result.

Relearn emails in the Junk folder as SPAM and in the cur folder as non-SPAM.

vi /etc/cron.d/spamassassin

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# m h dom mon dow user  command
13 3 * * * root /spamassassin-learn.sh

spamassassin-learn.sh

vi /spamassassin-learn.sh

#!/bin/sh

# Let spamassassin relearn the emails in the spam folder.
/usr/bin/sa-learn --spam /home/vmail/*/*/Maildir/Junk/cur 2>&1 >> /var/log/spamassassin-lean.log

# Let spamassassin relearn the emails in the cur folder. /usr/bin/sa-learn --ham /home/vmail///Maildir/cur 2>&1 >> /var/log/spamassassin-lean.log