OpenSMTPD Review, Pricing & Features

OpenSMTPD review covering the free, open-source OpenBSD SMTP server's features, security design, pricing, and alternatives like Postfix and Exim.

Category
Communication
Pricing
Open Source, from Free
Verified
Not yet
Last updated
July 19, 2026
Founded
2013
Headquarters
Open source project (OpenBSD)
Open SourceSelf-Hosted

Overview

OpenSMTPD is a free, open-source SMTP mail server daemon developed within the OpenBSD project, first publicly released in March 2013 after development beginning in late 2008. It was created to offer a simpler, more auditable, and more secure alternative to existing SMTP daemons.

It is maintained primarily by Gilles Chehade, Eric Faurot, and Charles Longeau, and is distributed under the ISC license, with a portable version supporting NetBSD, FreeBSD, DragonFly BSD, and various Linux distributions in addition to native OpenBSD.

Key Features

OpenSMTPD supports local mail delivery, relaying to other SMTP servers, authenticated mail submission, and receiving mail for virtual domains, covering the most common mail-server deployment scenarios.

Its security design includes strict input validation, bounded-buffer string handling, and privilege separation across processes, along with a deliberately simplified configuration syntax compared to larger daemons like Postfix or Exim.

Pricing

OpenSMTPD is entirely free and open source under the ISC license, with no licensing fees for deployment on any number of servers.

As a component of the OpenBSD project rather than a commercial vendor, there are no paid tiers, support contracts, or enterprise editions offered directly by the project itself.

Key Features

Pros & Cons

Pros

  • Completely free and open source under the permissive ISC license
  • Strong security-first design with privilege separation and strict input validation
  • Simple, auditable codebase compared to larger mail daemons
  • Easy-to-write configuration syntax
  • Backed by the security-focused OpenBSD project's development practices

Cons

  • Fewer advanced features than mature daemons like Postfix or Exim
  • Smaller community and third-party documentation base
  • No official commercial support offering from the project itself
  • Less common in large-scale enterprise mail deployments than Postfix
  • Niche or highly customized mail-routing setups may be harder to achieve

Pricing

Frequently Asked Questions

Is OpenSMTPD free?

Yes, OpenSMTPD is free and open source under the ISC license.

Who develops OpenSMTPD?

It is developed primarily by Gilles Chehade, Eric Faurot, and Charles Longeau as part of the OpenBSD project.

When was OpenSMTPD first released?

It was publicly released as version 5.3 on March 17, 2013, after development beginning in late 2008.

Can OpenSMTPD run on Linux?

Yes, an official portable version supports Linux distributions as well as NetBSD, FreeBSD, and DragonFly BSD in addition to native OpenBSD.

What makes OpenSMTPD different from Postfix or Exim?

OpenSMTPD deliberately implements a smaller, simpler feature set focused on security and ease of configuration, rather than the extensive configurability of Postfix or Exim.

Is OpenSMTPD suitable for production mail servers?

Yes, it supports local delivery, relaying, authenticated submission, and virtual domains, covering the most common production mail-server use cases.

What are the main alternatives to OpenSMTPD?

The main alternatives are Postfix, Exim, Sendmail, and qmail.

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