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Rspamd

rspamd.com

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Spec score 8.9 #2 of 35 in Email Security Gateways

What it 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. Authentication checks cover SPF, DKIM, DMARC, and ARC; malware scanning can use ClamAV or commercial antivirus engines. Administrators can define custom rules through the Lua API and configurable maps and selectors. Rspamd works with mail transfer agents including Postfix, Exim, and Sendmail, and its ClickHouse and Elasticsearch integrations provide visibility into attack patterns and detection rates. It is designed for gateway deployment and can run on-premises, keeping message data in the operator's environment without a mandatory vendor cloud. The detection engine is open source under Apache 2.0 and is available for Linux, macOS, and self-hosted use. Rspamd says its event-driven C core scans hundreds of messages per second per core and can scale from a single server to billions of messages a day. The open-source engine is listed at free. Scale costs £100 a month, with 5K mailboxes; hosted and enterprise plans have custom pricing. Premium plans offer support from core engineers, with enterprise SLA options.

Spec sheet

What it does
Rspamd is a high-performance daemon that analyzes email beside a mail-transfer agent and returns a spam score and recommended action.Read 15 Oct 2026 · docs.rspamd.com
Purpose
Rspamd is an email security engine designed to stop phishing, business email compromise, malicious attachments, and spam.Read 7 Oct 2026 · rspamd.com
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.Read 7 Oct 2026 · rspamd.com
License
The project is licensed under Apache License 2.0, allowing commercial use, modification and redistribution with no warranty.Read 15 Oct 2026 · docs.rspamd.com
Company
The site identifies the company as Rspamd Ltd.Read 7 Oct 2026 · rspamd.com
AI integrations
The documented feature set includes GPT integration, custom HTTP classifiers and verdict aggregation with existing rules.Read 15 Oct 2026 · docs.rspamd.com
Analytics integrations
Rspamd can export scan data to ClickHouse, Elasticsearch and custom webhooks.Read 15 Oct 2026 · docs.rspamd.com
Antivirus integrations
The antivirus module supports scanners including ClamAV, Kaspersky, Sophos, Avast, Avira, MetaDefender Cloud and VirusTotal.Read 15 Oct 2026 · docs.rspamd.com
Authentication
Its sender authentication checks include SPF, DKIM, DMARC, and ARC.Read 7 Oct 2026 · rspamd.com
Bayesian classifier
Bayes classification uses token statistics, Redis storage, per-user training and optional automatic learning.Read 15 Oct 2026 · docs.rspamd.com
Company headquarters
Crunchbase lists RSPAMD LTD in Cambridge, Cambridgeshire, United Kingdom.Read 15 Oct 2026 · crunchbase.com
Company legal name
Crunchbase identifies the legal name as RSPAMD LTD, an active private for-profit company.Read 15 Oct 2026 · crunchbase.com
Company size
Crunchbase lists the company size as 1–10 employees.Read 15 Oct 2026 · crunchbase.com
Custom rules
Rspamd supports custom filtering rules through its Lua API and configurable maps and selectors.Read 7 Oct 2026 · rspamd.com
Documentation depth
Documentation includes installation, configuration, modules, workers, tutorials, developer architecture and protocol material, a Lua API reference and FAQ.Read 15 Oct 2026 · docs.rspamd.com
Email authentication
Rspamd validates SPF, DKIM, DMARC and ARC, including cryptographic signing capabilities.Read 15 Oct 2026 · docs.rspamd.com
Filtering
It combines reputation, sender authentication, content analysis, and machine learning to score and filter messages.Read 7 Oct 2026 · rspamd.com
Filtering methods
The system combines Bayesian statistics, neural networks, fuzzy hashing, DNS blocklists and rule-based content checks.Read 15 Oct 2026 · docs.rspamd.com
Greylisting
Greylisting temporarily rejects unknown sender-recipient pairs and keeps triplet state in Redis.Read 15 Oct 2026 · docs.rspamd.com
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.Read 15 Oct 2026 · services.addons.thunderbird.net
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.Read 15 Oct 2026 · lowendtalk.com
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.Read 15 Oct 2026 · virusbulletin.com
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.Read 15 Oct 2026 · brokkr.net
Lua extensibility
Its Lua API exposes message contents, asynchronous Redis/HTTP/DNS operations, task changes, configuration and logging for custom plugins and rules.Read 15 Oct 2026 · docs.rspamd.com
Mail server integrations
Rspamd can work with mail transfer agents including Postfix, Exim, and Sendmail.Read 7 Oct 2026 · rspamd.com
Malware scanning
Rspamd can integrate with ClamAV and commercial antivirus engines to detect malware and dangerous attachment types.Read 7 Oct 2026 · rspamd.com
Module architecture
Four modules are compiled in C while many others are Lua plugins, and local plugins can be installed under the configuration plugin directory.Read 15 Oct 2026 · docs.rspamd.com
Neural detection
The neural module learns combinations of rule symbols and requires Redis to store its weights.Read 15 Oct 2026 · docs.rspamd.com
Notable news: premium service
A November 22, 2024 project mailing-list announcement introduced commercial premium fuzzy-storage access and premium lists.Read 15 Oct 2026 · lists.rspamd.com
Package support limit
The documentation says support for the previous stable branch ends when a new major release becomes stable and that old releases are not supported.Read 7 Oct 2026 · docs.rspamd.com
Praise: add-on usefulness
Thunderbird reviewers described the add-on as convenient, informative and useful for training spam and ham folders.Read 15 Oct 2026 · services.addons.thunderbird.net
Praise: consolidation
An independent deployment article reported replacing Policyd-SPF, OpenDKIM and OpenDMARC because Rspamd provided those functions together.Read 15 Oct 2026 · words.bombast.net
Praise: performance
A Linode community user described Rspamd as fast, accurate, auto-learning and able to replace several separate mail-filtering daemons.Read 15 Oct 2026 · linode.com
Praise: resource use
Heartbeats reported roughly 300 messages per minute using about 20% of two vCPUs and under 200 MB additional memory in its deployment.Read 15 Oct 2026 · heartbeats.jp
Premium support
Premium plans offer support from Rspamd's core engineers, with SLA options for enterprise users.Read 7 Oct 2026 · rspamd.com
Pricing basis
Pricing is based on the number of protected mailboxes, with the site estimating around 20 emails per mailbox per day as a rule of thumb.Read 7 Oct 2026 · rspamd.com
Public API
Rspamd exposes an HTTP/JSON scanning and controller API and also supports Milter, RSPAMC and spamc protocols.Read 15 Oct 2026 · docs.rspamd.com
Rate limiting
Rate limits can be applied by IP, sender, recipient or custom selector with tiered bucket limits backed by Redis.Read 15 Oct 2026 · docs.rspamd.com
Rating on Thunderbird Add-ons
4 out of 5 stars from 8 reviews for the Rspamd-spamness add-on.Read 15 Oct 2026 · services.addons.thunderbird.net
Reputation controls
Reputation tracking can cover sender IPs, URLs, DKIM and SPF domains and stores data in Redis or DNS lists.Read 15 Oct 2026 · docs.rspamd.com
Scale
Rspamd says its event-driven C core scans hundreds of messages per second per core and can scale from one server to billions of messages a day.Read 7 Oct 2026 · rspamd.com
Security release
Rspamd 4.2.1 fixed multiple critical memory-safety issues including HTTP heap overflow, use-after-free and out-of-bounds-write bugs.Read 15 Oct 2026 · github.com
Security updates
The documentation says security updates are released for the latest stable series and older stable series do not receive backports.Read 15 Oct 2026 · docs.rspamd.com
Self-hosting
Rspamd is designed to run on the operator's infrastructure and can be deployed with packages, Docker or Kubernetes-oriented setups.Read 15 Oct 2026 · docs.rspamd.com
Support channels
Community help is offered through GitHub, Discord, Telegram and mailing lists, while commercial support is available for large or custom deployments.Read 15 Oct 2026 · docs.rspamd.com
System prerequisites
The getting-started guide lists a supported Linux or BSD host or Docker, root access, Redis, a local recursive DNS resolver and an MTA.Read 15 Oct 2026 · docs.rspamd.com
Training limitation
Bayes produces no result until at least 200 spam and 200 ham messages have been learned, and neural detection also needs training data.Read 15 Oct 2026 · docs.rspamd.com
Usage-policy limit
The project asks users to contact it before embedding Rspamd in commercial or open-source projects and reserves the right to restrict service access.Read 15 Oct 2026 · docs.rspamd.com

Plans and prices

Open-source Rspamd Free Open-source engine · self-hosted Read 15 Oct 2026 · rspamd.com
Scale £100 a month £100 + VAT/month 5K mailboxes · scalable to your demands Read 7 Oct 2026 · rspamd.com
Scale £100 a month £100 + VAT/month 5K mailboxes · scalable to your demands · premium fuzzy database and bulk service Read 15 Oct 2026 · rspamd.com
Enterprise Priced on request Custom 50K+ mailboxes · Rspamd Console · neural/FastText models · priority support and SLA · custom development and training Read 15 Oct 2026 · rspamd.com
Hosted Priced on request Custom Custom mailboxes · fully managed deployment · runs on customer or Rspamd infrastructure Read 15 Oct 2026 · rspamd.com

Every Rspamd plan and price →

Strong points and limits

Strong points

  • Open-source detection engine is licensed under Apache 2.0.
  • Runs on-premises without mandatory vendor cloud dependency.
  • Checks SPF, DKIM, DMARC, and ARC.
  • Supports custom filtering through Lua, maps, and selectors.
  • Works with Postfix, Exim, and Sendmail.

Limits

  • Scale costs £100 a month.
  • Hosted and Enterprise pricing is custom.
  • Previous stable-branch support ends when a new major release is stable.
  • Old releases are not supported.

Who it suits

Rspamd suits organizations operating their own mail systems and seeking gateway filtering with control over message data and custom rules. Paid support and SLA options may suit larger deployments.

Rspamd in depth

Read the full write-up

Rspamd is a mail security gateway for teams that operate their own email infrastructure. It is strongest for administrators who want to tune filtering and keep message data on-premises; its open-source core is the main draw, while managed deployment and premium support come at a higher, mailbox-based cost.

Overview

Rspamd scores and filters messages using reputation, sender authentication, content analysis and machine learning. It targets spam, phishing, business email compromise and malicious attachments, and also supports outbound filtering and impersonation protection. That breadth makes it a gateway for broader mail security, not merely a junk-mail filter.

Deployment is on-premises, with no mandatory vendor cloud dependency, so message data can stay within the operator's environment. The Apache 2.0 detection engine integrates with Postfix, Exim and Sendmail, making it a natural fit for organizations already running those mail transfer agents. ClickHouse and Elasticsearch integrations add visibility into attack patterns and detection rates.

Key features

Layered detection: Reputation, authentication, message content and machine learning all contribute to scoring. This gives mail operators multiple signals to tune rather than relying on a single filtering method.

Authentication checks: SPF, DKIM, DMARC and ARC checks help evaluate sender legitimacy, which is useful alongside content and reputation analysis.

Malware integrations: ClamAV and commercial antivirus engines can be integrated to detect malware and dangerous attachment types. Teams can add scanning to their existing mail-security setup rather than treating spam filtering as the whole job.

Custom rules: A Lua API, maps and selectors let administrators adapt filtering to their environment. That flexibility is valuable when standard rules are not enough, but it favors teams able to maintain configuration.

Scale: Rspamd says its event-driven C core scans hundreds of messages per second per core and can scale from one server to billions of messages a day. The claimed range supports deployments from a single host to very large mail volumes, though the operator remains responsible for running the system.

Pricing

Pricing is based on protected mailboxes, with roughly 20 emails per mailbox per day offered as a rule of thumb. That makes mailbox count the key budgeting input, even where actual message volumes differ.

Open-source Rspamd — free: The Apache 2.0 engine is self-hosted and costs nothing. It suits teams with the skills to deploy and operate filtering themselves; this plan does not include the paid managed deployment or premium support offers.

Scale — £100 a month: The £100 + VAT/month plan covers 5K mailboxes and can scale to demand. It is the published-price option for operators needing paid capacity; VAT raises the payable amount, and the mailbox basis matters when estimating fit.

Hosted — custom pricing: Custom mailbox counts with managed deployment on either your infrastructure or Rspamd's. It suits organizations that want deployment help rather than managing the service entirely themselves.

Enterprise — custom pricing: For 50K+ mailboxes, with priority support and SLA options. This is aimed at large operators for whom support commitments are part of the buying decision.

Premium plans include support from Rspamd's core engineers, with SLA options for enterprise users. One operational caveat applies regardless of plan: support for a previous stable branch ends when a new major release becomes stable, and older releases are not supported. Teams that need long-term support for an older release should look elsewhere.

Platforms

Rspamd is available for Linux, macOS and self-hosted deployments. Its gateway model and mail-server integrations point to infrastructure operators rather than end users seeking a desktop or mobile mail app.

Who it's for

Rspamd suits mail administrators and organizations that want control over filtering rules, local data handling and integration with an existing mail-transfer stack. The free engine makes it accessible to teams comfortable with self-hosting; paid tiers offer a route to managed deployment or engineer support as mailbox scale grows. It is less suitable for teams seeking a turnkey cloud service or continued support for old stable branches.

Pros and cons

Pro: On-premises operation avoids a mandatory vendor cloud, which lets operators keep message data in their own environment.

Pro: Open-source licensing and custom Lua rules offer flexibility without an engine license fee.

Pro: Authentication, malware scanning integrations, outbound filtering and impersonation protection cover more than inbound spam.

Con: The flexibility and self-hosted gateway model place deployment and operational responsibility on the customer unless choosing a hosted plan.

Con: Only the Scale tier has a stated price; hosted and enterprise deployments require custom pricing, complicating budget comparisons.

Con: Old releases are unsupported, and a previous stable branch loses support when a new major release becomes stable.

Alternatives

For a different approach, consider Apache SpamAssassin, a free, open-source command-line filtering toolset for Linux and self-hosted use. Choose it when a free command-line filter is a better match than Rspamd's gateway-oriented engine and paid deployment options.

MailWasher offers a free plan for one email account with no support, plus a paid Pro plan; its Android, iOS and Windows platforms make it a more relevant comparison for users seeking a client-side option.

MX Guarddog charges $0.25 a month per email address, with no charge for user or domain aliases and no limit on addresses or messages. It is worth considering when per-address pricing and a web-based service suit better than self-hosting.

Cleanmail is another paid option with a free trial and self-hosted and web platforms. JetEmail has a free tier that does not expire, capped at 1,000 subscribers and 1 GB of image storage, as well as a $29.00 per month Starter plan; its API and web platforms make it a different kind of email service. Retarus Transactional Email offers a 30-day free trial capped at 5,000 emails and 200 emails per hour, with no load testing; it is a paid API and web option for transactional email. Sophos Secure Message offers paid email security plans and a free trial. Mailprotector offers a free email security check and paid products with pricing available from an account manager.

Browse Email Anti-Spam Software or Email Security Gateways for more options in those categories.

Verdict

Choose Rspamd if you operate your own mail infrastructure and want a configurable, open-source gateway that keeps message data on-premises. Its layered filtering, integrations and free core are compelling; look elsewhere if you need turnkey cloud operation or support for older releases.

Verdict

Rspamd gives mail operators an on-premises filtering engine with customizable rules and integrations for mail servers and analytics. Its core is free, while paid options add managed deployment or premium support at listed or custom prices.

Where Specifiction places it

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