Best Self Hosted Alternatives to Postfix

Haraka is an open source, event-driven SMTP server written in Node.js. It is designed for high throughput and concurrency, and is commonly deployed as a filtering MTA or mail submission agent (MSA) via a flexible plugin system.

Key Features

• Modular plugin architecture to customize SMTP behavior and mail processing
• High-performance asynchronous design suitable for thousands of concurrent connections
• Built-in outbound delivery and queueing for authenticated/relayed messages
• Supports common email authentication and policy needs via plugins (for example DKIM and SPF)
• Useful as a filtering layer alongside a separate mail store and IMAP server

Use Cases

• Run a high-throughput SMTP front-end with custom filtering and routing rules
• Deploy an MSA on port 587 with authentication and outbound signing policies
• Add specialized anti-spam and validation logic in front of an existing mail system

Haraka is a strong fit when you want a programmable SMTP server that is easy to extend in JavaScript and integrates with existing mail storage and IMAP solutions. Its plugin ecosystem enables practical customization without modifying the core server.

DragonFly Mail Agent (dma) is a small Mail Transfer Agent (MTA) designed for home and office use. It accepts mail from locally installed Mail User Agents and delivers messages either to local mailboxes or to remote SMTP destinations. Remote delivery includes TLS/SSL support and SMTP authentication.

Key Features

• Lightweight, C-based MTA focused on local submission and outbound delivery
• Local delivery to system mailboxes and forwarding to remote SMTP servers
• TLS/SSL support and SMTP authentication for secure remote delivery
• Does not listen on port 25; intended as a simple MTA rather than a full internet-facing server
• Simple installation and configuration with sendmail-compatible links and basic mail queue tools

Use Cases

• Provide an outbound relay for desktops, servers, or a home network
• Deliver system and application notifications to local mailboxes
• Offer a minimal MTA for small offices or embedded systems where full-featured MTAs are unnecessary

Limitations and Considerations

• Not intended to replace full-featured MTAs; lacks many advanced features such as inbound SMTP on port 25, extensive routing/virtual hosting, and advanced filtering
• Limited scalability for high-volume or enterprise mail infrastructures

DragonFly Mail Agent is a pragmatic, minimal MTA for environments that need simple local delivery and secure remote relay. It is best suited where low resource usage and straightforward configuration are priorities.

Sendmail Open Source is the open-source subset of Proofpoint's Sendmail Sentrion platform, designed for large and complex mail environments. The current Open Source release is Sendmail 8.16.1, distributed as a tar.gz archive with a PGP signature, and signed by the 2025 signing key. OpenDKIM is referenced as part of the Open Source offering.

Key Features

• Open Source subset of Sendmail Sentrion for enterprise-scale environments.
• Release 8.16.1 available on ftp.sendmail.org as a tar.gz archive with a PGP signature; signatures generated with the 2025 signing key.
• Includes OpenDKIM integration (DKIM) to authenticate messages.
• Security and licensing guidance, including CERT contact points and PGP signing keys.

Use Cases

• Deployments in large, complex mail infrastructures needing a durable open-source MTA with long-term manageability (virtualization, consolidation, cloud migration).
• Environments requiring verifiable, signed open-source builds from ftp.sendmail.org for audits and compliance.
• Setups needing DKIM-based mail signing and authentication controls.

Limitations and Considerations

• The Open Source option is a subset of the full Sendmail Sentrion offering; some enterprise features may be unavailable. Consult a specialist to assess fit.

Conclusion

Sendmail Open Source provides an officially supported open-source path for enterprise-style email deployments within the Sendmail Sentrion lineage. It offers a current release (8.16.1) with signed distributions and OpenDKIM support, suited for organizations able to manage an open-source MTA stack.

chasquid is an SMTP (email) server designed to send and receive mail like a traditional MTA, with an emphasis on simplicity, secure defaults, and ease of operation. It is aimed primarily at individuals and small groups who want a manageable mail server without excessive complexity.

Key Features

• SMTP server for sending and receiving email (MTA functionality)
• Secure-by-default behavior to avoid harmful misconfiguration (for example, preventing open relays and clear-text authentication)
• Multiple and virtual domains with per-domain users and aliases
• Support for address suffix dropping (user+tag@domain to user@domain)
• Dovecot integration for authentication
• Hooks for integrating greylisting, anti-virus, anti-spam, and DKIM/DMARC tooling
• SPF and MTA-STS checking
• Per-domain tracking of TLS support to prevent downgrade attacks
• Multiple TLS certificates and easy integration with Let's Encrypt
• Monitoring HTTP server with exported variables and tracing for debugging

Use Cases

• Running a small personal or family email server with safer defaults
• Hosting mail for a small organization with multiple domains and aliases
• Replacing heavier MTAs (such as Postfix or Exim) where simpler operation is preferred

Limitations and Considerations

• Not intended to replicate the full breadth of features and ecosystem integrations typical of very large-scale MTAs

chasquid provides a pragmatic SMTP server focused on operational simplicity while maintaining strong security practices. It is a solid fit when you need a traditional MTA with modern security checks and minimal administrative overhead.

OpenSMTPD is an open-source implementation of the server-side SMTP protocol (RFC 5321) originally developed as part of the OpenBSD project. It provides a minimal, security-focused mail transfer agent with a compact configuration model, extensible table backends and a filters API for mail processing.

Key Features

• Implements SMTP and common extensions with an emphasis on correctness and RFC compliance.
• Small, modular C daemon designed with privilege separation and process isolation to reduce attack surface.
• Declarative smtpd.conf with expressive match/action rules and built-in table support (examples in the codebase include passwd, sqlite and ldap table backends).
• Filters API and external filter/queue helpers allow integration of greylisting, DKIM signing, Rspamd, and other processing as separate components.
• Delivery options include maildir and mbox formats, an MDA helper, and LMTP client support for local delivery.
• TLS support via libtls/libressl with compatibility for OpenSSL builds, and per-listener TLS/cipher configuration options.
• Portable distribution and an "extras" set of table/filter modules allow packaging for non-OpenBSD systems while keeping the core minimal.

Use Cases

• Host SMTP for small organizations or single-host mail services that prioritize a small, auditable codebase.
• Deploy as a mail gateway/relay that enforces policy via filters and external scanners (spam, DKIM, greylisting).
• Integrate with system account stores or directory services using table backends (passwd, sqlite, LDAP) for virtual users and lookups.

Limitations and Considerations

• Advanced features such as DKIM signing, comprehensive anti-spam, or virus scanning are typically provided via external filters or proxies rather than baked into the core; administrators must deploy and configure filter components for those functions.
• Historical security advisories (patched in later releases) demonstrate the need to track upstream security fixes and apply updates promptly for exposed versions.
• The project prefers LibreSSL/libtls but supports OpenSSL; TLS behavior and available cipher/protocol features can vary depending on the TLS library used.

OpenSMTPD is a focused, security-oriented MTA that favors clarity and modularity. It is well suited for administrators who want a small, auditable mail server core and to assemble additional functionality via filters and table backends.