Instalar SpamAssassin on CentOS

How to install SpamAssassin on a CentOS 6 VPS

The following article is part 4 of our mailserver set-up with virtual users and domains using Postfix and Dovecot on a CentOS 6 VPS, followed by part 2 which explains how to install and set-up the Roundcube webmail interface on a linux vps server and then part 3 which is all about how to set-up an SSL encrypted connection in Postfix, Dovecot and Apache using SSL certificates.

In this tutorial we are going to set-up SpamAssassin on one of our CentOS 6 linux virtual servers and integrate it into our Postfix mailserver set-up so it can scan and mark the emails detected as SPAM.
What is SpamAssassin?
It is a program released under the Apache License 2.0 used for e-mail spam filtering based on content-matching rules.

UPDATE THE SYSTEM

As usual, make sure your CentOS 6 linux vps is fully up to date by executing:

## screen -U -S spamc-screen
## yum update

INSTALL SPAMASSASSIN

Install the SpamAssassin package using yum by running:

## yum install spamassassin

SET-UP USER

create spamfilter group used for the user that will run the spamassassin service

## groupadd spamfilter

create new user spamfilter with a home directory of /usr/local/spamassassin and add it to the spamfilter group you just created

## useradd -g spamfilter -s /bin/false -d /usr/local/spamassassin spamfilter
## chown spamfilter: /usr/local/spamassassin

CONFIGURE SPAMASSASSIN

next, configure spamassassin by editing /etc/mail/spamassassin/local.cf and adding/setting the following

## vim /etc/mail/spamassassin/local.cf

## Required_hits: This determines the filter balance; the lower the score the more aggressive the filter.
# A setting of 5.0 is generally effective for a small organisation or a single user.
# Adjust the strictness score to your organization's needs - a large medical organisation might want  to let email items
# through that are trying to sell pharmaceuticals, so we might increase the level to a more modest 8.0.
required_hits 5
## Report_safe:  This line determines whether to delete the item or to move the item to the inbox whilst appending
# a spam notice to the subject line. The levels for this line are set to either a 1 or 0. A score of 1 will delete the spam item,
# whereas a score of 0 will send the item to the inbox and rewrite the subject line.
report_safe 0
rewrite_header Subject [**SPAM**]
## Required_score: This line sets the spam score for all email allowed through to your domain, with levels of certainty set from 0 to 5.
# Zero would be classified as a legitimate email item, whereas 5 would be an definite 'SPAM' item.  If we set the score to 3 we would catch a
# lot of unsolicited emails but quite a few false positives would still get through. For our example email server we will use the score of 5,
# but you can of course set this value according to your preference.
required_score 5.0

before we proceed with starting-up the spamassassin service, we need to make sure it runs with our newly created spamfilter user by editing /etc/sysconfig/spamassassin and setting-up the following:

## vim /etc/sysconfig/spamassassin

# Options to spamd
SAHOME="/usr/local/spamassassin"
SPID_DIR="/var/run/spamassassin"
SUSER="spamfilter"
SPAMDOPTIONS="-d -c -m5 --username ${SUSER} -H ${SAHOME} -s ${SAHOME}/spamfilter.log"

with all that in place, we are ready to start and enable the spamassassin service on system startup using:

## service spamassassin start
## chkconfig spamassassin on

Fuente: https://www.rosehosting.com/blog/how-to-install-and-integrate-spamassassin-with-postfix-on-a-centos-6-vps/