Rspamd

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What Rspamd is

Rspamd is an email security engine for filtering phishing, business email compromise, malicious attachments, and spam. It scores messages using reputation, sender authentication, content analysis, and machine learning. Checks cover SPF, DKIM, DMARC, and ARC; malware detection can integrate with ClamAV and commercial antivirus engines. It works with mail transfer agents such as Postfix, Exim, and Sendmail, and lets administrators shape filtering with a Lua API, maps, and selectors. ClickHouse and Elasticsearch integrations provide visibility into attack patterns and detection rates. Designed for gateway deployment, it can run on-premises so message data stays in the user's environment, without a required vendor cloud. The detection engine is open source under Apache 2.0. Rspamd describes its event-driven C core as scanning hundreds of messages per second per core and scaling from one server to billions of messages a day. The free open-source engine is available, while Scale is £100 + VAT/month for 5K mailboxes; pricing is based on protected mailbox count. Premium plans offer support from core engineers, with SLA options for enterprise users.

Who it suits

Rspamd suits organizations that operate their own mail systems and want control over gateway filtering and message data. Its custom rules and integrations may also suit teams with specific filtering or analytics workflows.

What it does well

Checks SPF, DKIM, DMARC, and ARC.
Supports custom rules through Lua, maps, and selectors.
Can run on-premises without a required vendor cloud.
Open-source engine is licensed under Apache 2.0.
Works with Postfix, Exim, and Sendmail.

What to know first

Scale starts at £100 + VAT/month.
Pricing is based on protected mailbox count.
Old releases are not supported.
Previous stable branch support ends when a new major release becomes stable.

Plans

Plan	Billed and limits	Price
Open-source Rspamd	Open-source engine · self-hosted	Free
Scale	£100 + VAT/month · 5K mailboxes · scalable to your demands · premium fuzzy database and bulk service	£100 a month
Enterprise	Custom · 50K+ mailboxes · Rspamd Console · neural/FastText models · priority support and SLA · custom development and training	On request
Hosted	Custom · Custom mailboxes · fully managed deployment · runs on customer or Rspamd infrastructure	On request

As rspamd.com lists them, read 15 Oct 2026. The maker's own page has the final word.

Getting started

Visit https://rspamd.com/ for the project and plan details.
Choose the free self-hosted Open-source Rspamd plan or review the paid Scale, Hosted, and Enterprise options.
Deploy Rspamd on-premises as a mail gateway.
Connect it to a supported mail transfer agent such as Postfix, Exim, or Sendmail.
Configure filtering rules and any ClamAV, antivirus, ClickHouse, or Elasticsearch integrations you need.

Verdict

Rspamd offers a self-hosted email filtering engine with multiple authentication checks, malware integrations, and custom rule options. Consider its mailbox-based pricing and release support policy when evaluating it for a mail environment.

Questions

Is Rspamd free?

The Open-source Rspamd engine is free and self-hosted under Apache 2.0. Paid plans are also available.

How much does the Scale plan cost?

Scale costs £100 + VAT/month for 5K mailboxes and can scale to demand.

What do Hosted and Enterprise cost?

Both have custom pricing. Hosted offers managed deployment; Enterprise covers 50K+ mailboxes with priority support and SLA options.

Can Rspamd run on-premises?

Yes. It can run on-premises, with message data staying in the user's environment and no mandatory vendor cloud dependency.

Which mail transfer agents does it work with?

Rspamd can work with Postfix, Exim, and Sendmail.

Who makes Rspamd?

The site identifies the company as Rspamd Ltd.

Facts from Rspamd's own pages

AI integrations: The documented feature set includes GPT integration, custom HTTP classifiers and verdict aggregation with existing rules. · docs.rspamd.com, 15 Oct 2026
Analytics integrations: Rspamd can export scan data to ClickHouse, Elasticsearch and custom webhooks. · docs.rspamd.com, 15 Oct 2026
Antivirus integrations: The antivirus module supports scanners including ClamAV, Kaspersky, Sophos, Avast, Avira, MetaDefender Cloud and VirusTotal. · docs.rspamd.com, 15 Oct 2026
Authentication: Its sender authentication checks include SPF, DKIM, DMARC, and ARC. · rspamd.com, 7 Oct 2026
Bayesian classifier: Bayes classification uses token statistics, Redis storage, per-user training and optional automatic learning. · docs.rspamd.com, 15 Oct 2026
Company: The site identifies the company as Rspamd Ltd. · rspamd.com, 7 Oct 2026
Company headquarters: Crunchbase lists RSPAMD LTD in Cambridge, Cambridgeshire, United Kingdom. · crunchbase.com, 15 Oct 2026
Company legal name: Crunchbase identifies the legal name as RSPAMD LTD, an active private for-profit company. · crunchbase.com, 15 Oct 2026
Company size: Crunchbase lists the company size as 1–10 employees. · crunchbase.com, 15 Oct 2026
Custom rules: Rspamd supports custom filtering rules through its Lua API and configurable maps and selectors. · rspamd.com, 7 Oct 2026
Deployment: The project describes the engine as runnable on-premises, with message data staying in the user's environment and no mandatory vendor cloud dependency. · rspamd.com, 7 Oct 2026
Documentation depth: Documentation includes installation, configuration, modules, workers, tutorials, developer architecture and protocol material, a Lua API reference and FAQ. · docs.rspamd.com, 15 Oct 2026
Email authentication: Rspamd validates SPF, DKIM, DMARC and ARC, including cryptographic signing capabilities. · docs.rspamd.com, 15 Oct 2026
Filtering: It combines reputation, sender authentication, content analysis, and machine learning to score and filter messages. · rspamd.com, 7 Oct 2026
Filtering methods: The system combines Bayesian statistics, neural networks, fuzzy hashing, DNS blocklists and rule-based content checks. · docs.rspamd.com, 15 Oct 2026
Greylisting: Greylisting temporarily rejects unknown sender-recipient pairs and keeps triplet state in Redis. · docs.rspamd.com, 15 Oct 2026
License: The project is licensed under Apache License 2.0, allowing commercial use, modification and redistribution with no warranty. · docs.rspamd.com, 15 Oct 2026
Limit: add-on compatibility: Thunderbird reviewers reported that the add-on stopped working with Thunderbird 115.3.1 and that its instructions were difficult for non-programmers. · services.addons.thunderbird.net, 15 Oct 2026
Limit: administration effort: A LowEndTalk user who switched back to SpamAssassin said Rspamd required too much time and its user interface did not fit expected user workflows. · lowendtalk.com, 15 Oct 2026
Limit: malware detection: Virus Bulletin reported a 78.83% malware catch rate for Rspamd in its 2023 comparative test and called malware handling a challenge. · virusbulletin.com, 15 Oct 2026
Limit: setup complexity: A Postfix tutorial author found Rspamd poorly suited to a basic setup and said its many modules exposed inexperienced users to confusing configuration output. · brokkr.net, 15 Oct 2026
Lua extensibility: Its Lua API exposes message contents, asynchronous Redis/HTTP/DNS operations, task changes, configuration and logging for custom plugins and rules. · docs.rspamd.com, 15 Oct 2026
Mail server integrations: Rspamd can work with mail transfer agents including Postfix, Exim, and Sendmail. · rspamd.com, 7 Oct 2026
Malware scanning: Rspamd can integrate with ClamAV and commercial antivirus engines to detect malware and dangerous attachment types. · rspamd.com, 7 Oct 2026