Reliable anti-spam software is an important addition to everyone’s application collection irrespective of how the sensitivity level of the data that they handle because they exist to ensure that one’s inbox is not flooded with unsolicited messages, especially malicious ones.
Would you be surprised to know that 45% of all emails are spam? Well-established companies, for example, pay a lot of money to keep spam faraway from their digital borders because of the severe damage that a security bridge via spam can cause.
As induvial and small business owners, however, there isn’t really a need to spend remotely as much as large companies do thanks to the plethora of free and affordable options available in the market.
Today’s article focuses on the best open-source anti-spam software with which you can keep your custom email service as an individual or small business safe from annoying spam messages. They are all free, available to run on GNU/Linux platforms, and listed in alphabetic order.
1. Anti-Spam SMTP Proxy Server
Anti-Spam SMTP Proxy Server is an anti-spam tool that doubles as a full-fledged SMTP server for delivering mail. It is equipped with advanced algorithms that enable it to work like a man-in-the-middle between client software and SMTP in order to process emails, detect spam, and block them.
Feature Highlights
- Easy to set up from a web browser with minimal customization.
- Supports Mercury, Postfix, SendMail, and other popular SMTP servers.
- Option to not download attachments from specified lists.
- Supports SSL certificates for encrypting server-client connections.
- Integrates with FileScan and some other antivirus/antimalware software.
2. Bogofilter
Bogofilter is an interesting mail filtering tool for Linux. You can use this tool on the client computer for filtering spam messages. It doesn’t have tons of extra features built-in like other anti-spam tools. But it does an accurate job while flagging the spam mails.
The most interesting feature of this tool is its gradual learning technique. That means Bogofilter can learn from the user’s behavior apart from the preinstalled algorithms. This is why accuracy improves as you keep using this software.
Feature Highlights
- Completely free and open-source.
- Built-in support for GNOME, Evolution, KMail, and other popular email clients.
- Manually selecting emails as spam trains the app to filter illegitimate emails better.
- Detects spammy words and phrases in the mails using Oracle’s BerkeleyDB.
3. Hermes Secure Email Gateway
Hermes Secure Email Gateway works as a gateway that protects all incoming threats from your email server. It can easily be configured o Linux servers (e.g. Ubuntu) as it features a complete set of tools powered by third-party engines for virus and spam detection which are open-source. It includes Postfix and SpamAssassin, among other software for providing users with a secure mail environment.
Feature Highlights
- Completely free and open-source.
- A neat, web-based all-in-one dashboard with a UI that is easy to use.
- Checks emails in mailing services such as Google Workspace and Microsoft Office 365.
- Fully supports encryption protocols for enhanced security.
- Can be installed using a sh script with a storage archive in the cloud.
4. MailCleaner
MailCleaner is a powerful, feature-packed tool that can be installed as a gateway in front of mail servers. It is available as a commercial version with an annual subscription, and a community edition which, although has some limitations, is customizable to include required features thanks to it being open-source and based on Debian.
Feature Highlights
- Available as commercial and community editions.
- Supports integrating with third-party software for malware and virus protection.
- Integrates nicely with Google and Microsoft’s mail service and learns from users’ usage patterns.
- Block newsletters sent by companies using unethical email marketing strategies.
5. Mailfilter
Mailfilter is a feature-rich analyzer tool for easily filtering unwanted spam emails. It ships with predefined algorithms for spam detection and the option to specify rules for its detection engine. It also has the ability to connect to mail servers via POP in order to detect fishy emails before they’re downloaded to the client.
Feature Highlights
- Completely free and open-source.
- Detect and erase spam in emails directly from the server.
- Memory-friendly.
- Easy to set up and requires no technical/coding knowledge.
6. MailScanner
MailScanner is among the popular anti-spam tools know for its virus scanning feature for mail attachments. With a reported scanning records of over a billion emails daily, MailScanner is relied on by many (including even the US military) for scanning and disinfecting emails, especially when combined with Microsoft Outlook.
Feature Highlights
- Completely free and open-source.
- Modern, easy-to-use user interface.
- Supports several mail servers including Exim and SendMail.
- Fix virus-infected documents and automatically forward them to their destination.
- Supports several popular virus scanners.
7. Proxmox Mail Gateway
Proxmox Mail Gateway is a scalable, server-side management tool for emails that can be deployed on existing mail servers. It provides several protective functionalities among which is an antispam tool. While there exists a premium version, the community edition is free and open-source with enough features for small businesses.
Feature Highlights
- Available as a free and open-source version and a premium edition.
- Highly scalable for different market sizes with support for different clients and servers.
- Easy to deploy.
- Training guides and documentation available.
- Support for DNS-based blocking, customizable blacklisting, Bayesian check, etc.
- Monitor email traffic in real-time.
- Scan viruses and trojans using reliable databases and engines.
8. Rspamd
Rspamd is a powerful anti-spam tool targeted at large organizations as is evident from its simultaneous processing ability. My favorite feature is the fact that it assigns spam scores to different mails using several algorithms. This is coupled with its ability to learn which emails to exclude the more it is used.
Feature Highlights
- Completely free and open-source.
- Cohesive, Ajax-based user interface.
- Customizable rules for different senders with the option to override the section engine with a blacklist and whitelist.
- Trains itself to improve accuracy using a neural network.
- API supports modules written in Lua for extending functionality
9. Scrollout F1
Scrollout F1 is a modern, robust multi-platform spam detection software that works mainly as an email firewall. It consists of both a virus scanner and spam blocker complemented with complete freedom on the number of SMTP servers and emails.
Feature Highlights
- Completely free and open-source.
- Easy-to-use web-based UI with a built-in user guide.
- Block messages based on IP initials, location, and top-level domains.
- Block newsletter and promotional messages using built-in configurations.
- Supports drag and drop in Microsoft Outlook and similar clients.
- Supports email backups in remote server locations.
10. SpamAssassin
SpamAssassin detects and removes spammy emails before they arrive in your inbox. It is an advanced spam filtering tool that features several algorithms for efficiently detecting spams from their subject and body content with a 95% success rate.
Feature Highlights
- Completely free and open-source.
- Configurable using the configuration text file.
- Deployable API with support for popular email management tools.
- Supports DNS blocking for spam filtering as well as by tagging from the front-end mail client.
- Supports plugins.
As you have probably concluded by now, there is no need to panic about spam emails when you’ve got a GNU/Linux operating system running. The list contains reliable options for client computers as well as Linux servers – it is left to you to go with the one that appeals to you.
Are you a beginner to spam protection? Pick one of the simplest options to get started with but if you’re a techie then you’ll be doing no harm by jumping in the deep end.
Are there any anti-spam tools for Linux that we have left out? Feel free to tell us about them and their features in the comments section below.
