Email communication is an essential part of both business and personal life, but with increasing reliance on emails comes heightened risk of attacks such as spam, viruses, and phishing. For CentOS 7 system administrators, it's crucial to implement robust email security solutions. This article provides a detailed overview of the steps required to secure your email server.

Solution Overview

For effective email security on CentOS 7, we recommend a combination of the following components:

1. SpamAssassin: a filter for spam detection,
2. ClamAV: an antivirus program,
3. Amavis: an interface between SpamAssassin and ClamAV,
4. Postfix: a popular email server, which will serve as the foundation.

Installation and Configuration of Postfix

Let's start with installing Postfix, which will serve as our default MTA (Mail Transfer Agent).

1. Install Postfix:

   sudo yum install postfix
   ​

2. Set Postfix as the default MTA and start it:

   sudo systemctl enable postfix
   sudo systemctl start postfix
   ​

Installation and Configuration of SpamAssassin

SpamAssassin is an effective tool for detecting and filtering spam.

1. Install SpamAssassin:

   sudo yum install spamassassin
   ​

2. Activate and configure the SpamAssassin service:

   sudo systemctl enable spamassassin
   sudo systemctl start spamassassin
   ​

 

Installation and Configuration of ClamAV

ClamAV is an open-source antivirus tool designed to detect trojans, viruses, malware, and other malicious threats.

1. Install ClamAV:

   sudo yum install clamav clamd
   ​

2. Start the antivirus service and perform regular virus database updates:

   sudo freshclam
   sudo systemctl enable clamd@scan
   sudo systemctl start clamd@scan
   ​

 

Integration of Amavis

Amavis (A Mail Virus Scanner) serves as an interface between SpamAssassin and ClamAV.

1. Install Amavis:

   sudo yum install amavisd-new
   ​

2. Configure Amavis to use with ClamAV and SpamAssassin: Modify the configuration file /etc/amavisd/amavisd.conf to ensure Amavis uses ClamAV and SpamAssassin for email scanning.

Linking Postfix with Amavis

After configuring all components, it's necessary to link Postfix with Amavis to ensure all incoming and outgoing emails pass through the scanning process.

1. Edit the Postfix configuration file /etc/postfix/main.cf and add rules to route emails through Amavis.

Testing and Optimization

After completing the configuration, it's essential to thoroughly test the entire system and make any necessary optimizations, such as setting rules for SpamAssassin, updating virus databases for ClamAV, and performing regular system maintenance.

By implementing these steps, you'll secure your email system on CentOS 7 against spam, viruses, and phishing attacks, significantly reducing the risk of cyber threats and protecting sensitive information.