These days spam emails are a constant nuisance. They clog up our inboxes, waste our time, and can even pose a security threat. That's where SpamAssassin comes in.

SpamAssassin is a powerful open-source spam filter that uses a variety of techniques to identify and block spam emails. In this article, we'll dive into the world of SpamAssassin and explore how it works, its features, and how you can use it to keep your inbox spam-free.

What is SpamAssassin?

SpamAssassin is a free, open-source spam filter that uses a combination of techniques to identify and block spam emails. It was first released in 2001 and has since become one of the most popular spam filters in the world.

How Does SpamAssassin Work?

SpamAssassin uses a scoring system to determine whether an email is spam or not. It assigns points to various elements of an email, such as the sender's address, subject line, and content. If an email reaches a certain threshold of points, it is marked as spam and either deleted or sent to a designated spam folder.

SpamAssassin also uses a variety of techniques to identify spam, including:

  • Header Analysis: SpamAssassin looks at the email's header to check for suspicious elements, such as a fake sender address or a mismatched domain.
  • Content Analysis: The filter analyzes the content of the email for spam-like characteristics, such as excessive use of capital letters, misleading subject lines, or suspicious links.
  • Blacklists and Whitelists: SpamAssassin checks the sender's IP address against known blacklists of spammers and also allows users to create whitelists of trusted senders.
  • Bayesian Filtering: This technique uses statistical analysis to determine the probability of an email being spam based on its content and compares it to a database of known spam emails.

Installing Spam assassin

Spam assasin can be installed on any system. Here's a general guide for each:


Install Homebrew:

First, you need to have Homebrew installed, which is a package manager for macOS. If you don't have it, you can install it by running the following command in the Terminal:

Follow the on-screen instructions to complete the installation.

Install SpamAssassin:

Once Homebrew is installed, you can install SpamAssassin with the following command:

Configure and Run:

After installation, you can configure SpamAssassin by editing its configuration file, usually located at /usr/local/etc/mail/spamassassin. You can start SpamAssassin using:

Linux (Debian/Ubuntu)

Update Package List:

Install SpamAssassin:

Enable the SpamAssassin Service:

You can enable SpamAssassin by editing the /etc/default/spamassassin file and setting ENABLED=1. Start the service:


Configure SpamAssassin by editing /etc/spamassassin/


Installing SpamAssassin on Windows is a bit more complex as it's primarily designed for Unix-based systems. However, you can use it through Windows Subsystem for Linux (WSL) or use a virtual machine running a Linux distribution. Here's a brief guide for WSL:

Install Windows Subsystem for Linux (WSL):

Open PowerShell as Administrator and run:

Follow the instructions to install a Linux distribution from the Microsoft Store.

Update and Install SpamAssassin:

After setting up WSL with a Linux distribution (e.g., Ubuntu), open the Linux terminal and run:

Configure and Run:

Similar to the Linux installation, configure and run SpamAssassin within the WSL environment.

Remember, this is a basic guide, and you might need to perform additional steps depending on your specific setup and requirements. Always refer to the official documentation or community forums for detailed instructions and troubleshooting.

How to Use SpamAssassin

SpamAssassin can be used in a variety of ways, depending on your needs and preferences. Here are a few options for using SpamAssassin:

  • As a standalone program: You can download and install SpamAssassin on your computer or server and use it as a standalone program. This option is best for advanced users who are comfortable with command-line interfaces.
  • As part of an email server: Many email servers, such as Postfix and Sendmail, come with built-in support for SpamAssassin. This option is best for those who want to filter spam at the server level.
  • As a plugin for email clients: Some email clients, such as Thunderbird and Outlook, have plugins that allow you to use SpamAssassin to filter your emails. This option is best for those who want to filter spam at the client level.

Configuring spam config

Configuring SpamAssassin on a Linux terminal involves editing its configuration files and setting up various filters and rules. Here's a basic guide to get you started:

Access the Configuration File

SpamAssassin's main configuration file is typically located at . Open it with a text editor, for example, using nano:

Basic Configuration Options

Set the Required Score:

This is the score at which an email is considered spam. Example: To set the score to 5.0 (default is usually 5):

Use Bayesian Filtering:

This enables the Bayesian filter, which learns from spam and ham (non-spam) to improve accuracy. Enable it by adding:

Whitelisting and Blacklisting


To ensure emails from certain addresses are never marked as spam:


To always mark emails from specific addresses as spam:

Advanced Spam Filters

DNS Blocklists:

Use DNS-based blocklists to reject known spam sources.


Adjust Scoring for Specific Tests:

You can adjust the scores assigned to specific tests. Example: Increase score for a specific test:

Save and Restart SpamAssassin

After making changes, save the file and exit the editor. Restart SpamAssassin to apply the changes:

Testing SpamAssassin

To test if SpamAssassin is working correctly:

Send a Test Email:

Send an email with the following test string in the body:

This string is recognized by SpamAssassin as a guaranteed spam signature.

Check the Headers:

If SpamAssassin is working, the email headers should include information about the spam check, including the score and which tests were triggered.

Understanding the SpamAssassin Score

As mentioned earlier, SpamAssassin assigns points to various elements of an email to determine whether it is spam or not. The higher the score, the more likely it is that the email is spam.

The default threshold for marking an email as spam is 5 points, but this can be adjusted based on your preferences. You can also choose to have emails with a score between 5 and 10 sent to a designated spam folder, while emails with a score above 10 are deleted.

How to Check the SpamAssassin Score

If you're using SpamAssassin as a standalone program, you can check the score of an email by running it through the spamassassin command. If you're using SpamAssassin as part of an email server or client, the score will usually be displayed in the email's header.

Customizing SpamAssassin

One of the great things about SpamAssassin is its flexibility and customizability. You can adjust the filter's settings to fit your specific needs and preferences.

Whitelisting and Blacklisting

As mentioned earlier, SpamAssassin allows you to create whitelists and blacklists of senders. This is useful if you want to ensure that emails from certain senders are always marked as spam or never marked as spam.

Adjusting the Score Threshold

If you find that too many legitimate emails are being marked as spam, you can adjust the score threshold to be more lenient. On the other hand, if you're still receiving a lot of spam, you can lower the threshold to be more strict.

Creating Custom Rules

SpamAssassin also allows you to create custom rules to further refine its filtering capabilities. These rules can be based on a variety of criteria, such as specific words or phrases in the email's content or header.

Real-World Examples of SpamAssassin in Action

SpamAssassin is used by millions of individuals and organizations around the world to keep their inboxes free of spam. Here are a few real-world examples of how SpamAssassin has helped users combat spam:

The Apache Software Foundation

The Apache Software Foundation, a non-profit organization that supports open-source software projects, uses SpamAssassin to filter spam from its mailing lists. With over 300 mailing lists and thousands of subscribers, SpamAssassin has helped the foundation keep its communication channels spam-free.

The University of Oxford

The University of Oxford, one of the world's leading academic institutions, uses SpamAssassin to filter spam from its email servers. With over 20,000 students and staff, the university needed a powerful and reliable spam filter, and SpamAssassin fit the bill perfectly.


SpamAssassin is a powerful and versatile spam filter that can help you keep your inbox free of spam. With its variety of techniques and customizable settings, it can be tailored to fit your specific needs and preferences. Whether you're an individual or an organization, SpamAssassin is a valuable tool for keeping your email communication spam-free.