Install SpamAssassin with Postfix on Ubuntu 20.04

In this article, we’ll explain how to install SpamAssassin with Postfix on Ubuntu 20.04.

Apache SpamAssassin is the #1 Open Source anti-spam platform giving system administrators a filter to classify email and block spam (unsolicited bulk email). It uses a robust scoring framework and plug-ins to integrate a wide range of advanced heuristic and statistical analysis tests on email headers and body text including text analysis, Bayesian filtering, DNS blocklists, and collaborative filtering databases.

Prerequisites

• A Ubuntu installed server with Postfix
• A root user access or normal user with administrative privileges.

Install SpamAssassin with Postfix on Ubuntu

1. Keep the server up to date

# apt update -y && apt upgrade -y

2. Install SpamAssassin

Install SpamAssassin using following command.

# apt-get install spamassassin spamc -y

Add one user to assign to SpamAssassin and disable the login.

# adduser spamd –disabled-login

3. Configure SpamAssassin

Now let’s assign newly created user spamd to SpamAssassin and set the log and default home directories.

First, open SpamAssassin configuration file in editor.

# vim /etc/default/spamassassin

Find ENABLED=1 and uncomment it and set it to 0.

# ENABLED=0

Second, find OPTIONS= and add home directory and log file.

# OPTIONS=”–create-prefs –max-children 5 –username spamd –helper-home-dir /home/spamd/ -s /home/spamd/spamd.log”

Finally, find CRON=0 and set to 1.

# CRON=1

Now save and exit the file.

Take a back of SpamAssassin local configuration file and create a new SpamAssassin local configuration file using following command:

# mv /etc/spamassassin/local.cf /etc/spamassassin/local.cf.bk

# vim /etc/spamassassin/local.cf

Copy and paste following lines in the file:

rewrite_header Subject ***** SPAM _SCORE_ *****
report_safe             0
required_score          5.0
use_bayes               1
use_bayes_rules         1
bayes_auto_learn        1
skip_rbl_checks         0
use_razor2              0
use_dcc                 0
use_pyzor               0
ifplugin Mail::SpamAssassin::Plugin::Shortcircuit
endif

Save and exit the file.

4. Configure Postfix

1. Edit your Postfix configuration file.

# /etc/postfix/master.cf

2. Find following entries:

smtp      inet  n       -       y       -       -       smtpd
#smtp      inet  n       -       y       -       1       postscreen
#smtpd     pass  -       -       y       -       -       smtpd
#dnsblog   unix  -       -       y       -       0       dnsblog
#tlsproxy  unix  -       -       y       -       0       tlsproxy
submission inet n       -       y       -       -       smtpd

3. Below the smtp configuration, add a SpamAssassin content filter.

smtp      inet  n       -       y       -       -       smtpd

-o content_filter=spamassassin
spamassassin unix -     n       n       -       -       pipe
user=spamd argv=/usr/bin/spamc -f -e  
/usr/sbin/sendmail -oi -f ${sender} ${recipient}

Save and exit the file.

4. Restart Postfix and enable SpamAssassin to run at system startup.

# systemctl restart postfix.service
# systemctl enable spamassassin.service
# systemctl start spamassassin.service

That’s it. The installation and configuration process has been completed successfully.

In this article, we have explained how to install SpamAssassin with Postfix on Ubuntu 20.04.