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Apache SpamAssassin

spamassassin.apache.org

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Spec score 9.1 #1 of 28 in Email Anti-Spam Software

What it is

Apache SpamAssassin is free, open-source software that classifies email to help system administrators block unsolicited bulk messages. It runs on a server to filter mail before it reaches a mailbox. Detection combines header and text analysis, Bayesian filtering, DNS blocklists, collaborative filtering databases, and local and network tests. Its scoring framework and plugins add heuristic and statistical checks. Tests and configuration are stored as plain text, so administrators can adjust settings and add rules. The Mail::SpamAssassin API can be integrated with systems such as procmail, sendmail, Postfix, and qmail. The core distribution includes command-line filtering tools and Perl modules for use in other products. The downloads page lists version 4.0.2 as the released version. Official releases are signed, with GPG signatures and SHA-256 and SHA-512 checksum links for downloads. Users can ask questions on the mailing list; developers and PMC members answer as time permits.

Spec sheet

What it does
Apache SpamAssassin is an open-source filter that classifies email and blocks unsolicited bulk mail.Read 14 Oct 2026 · spamassassin.apache.org
Purpose
SpamAssassin classifies email and helps system administrators block unsolicited bulk email.Read 5 Oct 2026 · spamassassin.apache.org
Deployment
The project wiki says SpamAssassin runs on a server and filters spam before it reaches the mailbox.Read 5 Oct 2026 · cwiki.apache.org
API
The Mail::SpamAssassin classes expose an abstract API for embedding the engine in mail systems.Read 14 Oct 2026 · spamassassin.apache.org
Support
The user mailing list accepts questions, and developers and PMC members answer as time permits.Read 5 Oct 2026 · cwiki.apache.org
License
Apache SpamAssassin is free open-source software under the Apache License 2.0.Read 14 Oct 2026 · spamassassin.apache.org
Bayesian filtering
The software includes Bayesian learning that can be trained with ham and spam examples using sa-learn.Read 14 Oct 2026 · en.wikipedia.org
Command-line tools
The distribution includes filtering tools plus spamc, spamd, sa-learn, sa-update and sa-compile utilities.Read 14 Oct 2026 · spamassassin.apache.org
Company ownership
SpamAssassin is an Apache Software Foundation project rather than a commercial vendor product.Read 14 Oct 2026 · spamassassin.apache.org
Configuration
Anti-spam tests and configuration are stored in plain text, so users can configure the software and add rules.Read 5 Oct 2026 · spamassassin.apache.org
Current listed release
The downloads page lists version 4.0.2 as the released version.Read 5 Oct 2026 · spamassassin.apache.org
Current release
The official site lists Apache SpamAssassin 4.0.2, released on 2025-08-30.Read 14 Oct 2026 · spamassassin.apache.org
Detection methods
Its scoring framework combines heuristic and statistical tests on headers and message bodies.Read 14 Oct 2026 · spamassassin.apache.org
Distribution
The core distribution consists of command-line filtering tools and Perl modules for use in other products.Read 5 Oct 2026 · spamassassin.apache.org
Documentation depth
Documentation includes README, INSTALL, UPGRADE, spamd and SQL-preference guides, wiki material and versioned POD manuals.Read 14 Oct 2026 · spamassassin.apache.org
Download integrity
Official release archives provide GPG signatures and SHA-256 and SHA-512 checksums.Read 14 Oct 2026 · spamassassin.apache.org
Independent architecture
Wikipedia describes it as a Perl-based application that can run standalone, behind spamd, or inside mail-filter programs such as Amavis and MIMEDefang.Read 14 Oct 2026 · en.wikipedia.org
Independent feature gaps
SourceForge marks allow/block lists, audit logs, archiving, recovery, routing, encryption, fraud detection, quarantine, reporting and statistics as not supported.Read 14 Oct 2026 · sourceforge.net
Independent integrations listing
SourceForge lists Exim, GlockApps, KMail, Rad Web Hosting, Sekoia.io and SPanel as integrations.Read 14 Oct 2026 · sourceforge.net
Independent limitation
Wikipedia notes that heuristic classification can produce both false positives and false negatives.Read 14 Oct 2026 · en.wikipedia.org
Independent platform listing
AlternativeTo categorizes SpamAssassin for Linux, self-hosted, Windows, web and Mac environments.Read 14 Oct 2026 · alternativeto.net
Independent popularity
AlternativeTo shows 15 likes for SpamAssassin and labels it free and open source.Read 14 Oct 2026 · alternativeto.net
Independent review availability
SourceForge states that SpamAssassin had not been reviewed on its listing when accessed.Read 14 Oct 2026 · sourceforge.net
Independent training listing
SourceForge says the available training format is documentation.Read 14 Oct 2026 · sourceforge.net
Integration
Its Mail::SpamAssassin API can be integrated into email systems including procmail, sendmail, Postfix, and qmail.Read 5 Oct 2026 · spamassassin.apache.org
Limit: false positives
Project guidance says occasional false positives are unavoidable and recommends checking Bayes and AWL training when they recur.Read 14 Oct 2026 · cwiki.apache.org
Limit: learning curve
The same Reddit discussion describes self-managed filtering as requiring staff expertise and a significant initial learning curve.Read 14 Oct 2026 · reddit.com
Limit: maintenance effort
Accuracy guidance requires recent rule versions, daily sa-update runs, network tests and ongoing classifier training.Read 14 Oct 2026 · cwiki.apache.org
Limit: network dependence
The project says disabling network rules causes materially more incorrect classifications and recommends local caching DNS.Read 14 Oct 2026 · cwiki.apache.org
Mail integrations
Official documentation names procmail, sendmail, Postfix and qmail among supported mail-system integrations.Read 14 Oct 2026 · spamassassin.apache.org
Maker founded
SourceForge lists the Apache Software Foundation as founded in 1999.Read 14 Oct 2026 · sourceforge.net
Maker headquarters
The Apache Software Foundation lists its mailing address as 1000 N West Street, Suite 1200, Wilmington, Delaware, USA.Read 14 Oct 2026 · apache.org
Message-size limit
The spamassassin manual warns that messages above about 500 KB can consume very large amounts of memory.Read 14 Oct 2026 · spamassassin.apache.org
Network checks
Supported network techniques include DNS blocklists and whitelists, fuzzy checksums, SPF, DKIM and URI blocklists.Read 14 Oct 2026 · en.wikipedia.org
Notable deployment responsibility
The project advises system administrators to replace the default report template contact details with their own support desk information.Read 5 Oct 2026 · spamassassin.apache.org
Perl module
Mail::SpamAssassin is distributed as a Perl module and can be installed through CPAN.Read 14 Oct 2026 · spamassassin.apache.org
Plain-text rules
Rules and configuration are stored as plain text, allowing administrators to add or change tests.Read 14 Oct 2026 · spamassassin.apache.org
Plug-in architecture
SpamAssassin uses plug-ins and allows additional detection methods to be added through Perl plug-ins.Read 14 Oct 2026 · spamassassin.apache.org
Praise: operational performance
A Reddit mail-hosting operator reports that a tuned SpamAssassin stack handles millions of messages daily with fast delivery for clients.Read 14 Oct 2026 · reddit.com
Rating on SourceForge
0.0 out of 5 from 0 reviews.Read 14 Oct 2026 · sourceforge.net
Release compatibility
Version 4.0.2 adds compatibility with Perl 5.42 and newer required Perl modules.Read 14 Oct 2026 · spamassassin.apache.org
Release integrity
Official releases are signed with a GPG key, and each download has GPG signature and SHA-256 and SHA-512 checksum links.Read 5 Oct 2026 · spamassassin.apache.org
Scoring and plugins
It uses a scoring framework and plugins to incorporate heuristic and statistical tests.Read 5 Oct 2026 · spamassassin.apache.org
Security history
The project release notes document fixes for CVE-2020-1946 and earlier rule-file command-execution and denial-of-service vulnerabilities.Read 14 Oct 2026 · spamassassin.apache.org
Security reporting
The project asks people who find a security issue to email [email protected] or report it in Bugzilla with the Security component selected.Read 5 Oct 2026 · cwiki.apache.org
Self-hosting
The product is downloaded as source archives and operated by system administrators on their own mail infrastructure.Read 14 Oct 2026 · spamassassin.apache.org
Wide-spectrum tests
The project says it uses a variety of local and network tests to identify spam signatures.Read 5 Oct 2026 · spamassassin.apache.org

Plans and prices

Apache SpamAssassin Free Open-source software · command-line filtering tools and Perl modules Read 5 Oct 2026 · spamassassin.apache.org
Apache SpamAssassin Free Free software self-hosted mail filtering · administrator-managed configuration · no hosted service described Read 14 Oct 2026 · spamassassin.apache.org

Every Apache SpamAssassin plan and price →

Strong points and limits

Strong points

  • Free and open source
  • Combines Bayesian filtering and DNS blocklists
  • Plain-text rules and configuration can be adjusted
  • API supports several email systems
  • Release downloads include signature and checksum links

Limits

  • Runs on a server before mail reaches mailboxes
  • Mailing-list responses are provided as time permits
  • Current listed release is version 4.0.2

Who it suits

It suits system administrators who want a configurable, self-hosted email filter and can work with its command-line tools, Perl modules, or API.

Verdict

SpamAssassin offers several detection methods and configurable rules for server-side filtering. Administrators should account for its deployment and support model.

Where Specifiction places it

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