Bird Email API
Email sending API & SMTP relay with analytics and deliverability tooling
Open-Source Projects
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Discover top open-source software, updated regularly with real-world adoption signals.
High-performance Node.js SMTP server with modular plugin architecture
Haraka is a scalable, asynchronous email server built on Node.js that handles thousands of concurrent connections with extensible plugins for filtering, authentication, and relay.
Haraka is a high-performance email server built entirely in Node.js, designed to handle thousands of concurrent connections and deliver thousands of messages per second. Its asynchronous, event-driven architecture makes it exceptionally fast and resource-efficient compared to traditional mail transfer agents.
Unlike monolithic mail servers, Haraka's modular plugin system lets you compose exactly the functionality you need. Whether you're building a filtering MTA to protect existing mail infrastructure, running a mail submission agent with DKIM signing and authentication, or creating custom email workflows, plugins provide the building blocks. The ecosystem includes spam protection via SpamAssassin, DNS blocklist checking, HELO validation, and dozens more.
Haraka intentionally focuses on mail transfer and filtering rather than storage or retrieval. It's designed to work alongside systems like Postfix, Exchange, or Dovecot—complementing their strengths while adding powerful filtering and routing capabilities. The built-in outbound delivery engine automatically queues authenticated messages for relay. Installation via npm takes seconds, and configuration through simple text files and JavaScript plugins makes customization straightforward for developers familiar with the Node.js ecosystem.
When teams consider Haraka, these hosted platforms usually appear on the same shortlist.
Looking for a hosted option? These are the services engineering teams benchmark against before choosing open source.
Spam Filtering Gateway
Deploy Haraka in front of Exchange or Postfix to filter incoming mail through SpamAssassin, DNSBL checks, and custom rules before delivery to the mail store.
Application Email Relay
Enable SaaS applications to send transactional email through authenticated SMTP with automatic DKIM signing and outbound queue management.
Custom Address Routing
Implement qmail-style extended addressing (user-tag@domain.com) with a simple plugin to route tagged messages to base addresses in legacy systems.
Multi-Tenant Email Processing
Build per-customer email workflows with JavaScript plugins that parse, transform, and route messages based on domain-specific business logic.
No. Haraka focuses on mail transfer and filtering, not storage or IMAP. It's designed to work alongside systems like Postfix, Exchange, or Dovecot, typically as a filtering gateway or relay.
Haraka can handle thousands of concurrent connections and deliver thousands of messages per second thanks to its asynchronous Node.js architecture, though actual performance depends on plugins and hardware.
If you know JavaScript and Node.js, writing plugins is straightforward. Haraka's event-driven hooks let you intercept and modify mail flow at every stage with just a few lines of code.
Haraka includes plugins for SpamAssassin integration, DNS blocklists (DNSBL), SPF/DKIM validation, HELO checks, rate limiting, and many other anti-spam techniques available in the plugin ecosystem.
Yes. Haraka includes a scalable outbound delivery engine that automatically queues messages marked for relaying (typically via authentication plugins) and manages delivery with retry logic.
Project at a glance
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