OpenSMTPD

Free SMTP server implementation from the OpenBSD project.

About OpenSMTPD

OpenSMTPD is a free implementation of the server-side SMTP protocol, developed as part of the OpenBSD project. It lets ordinary machines send and receive email with other systems speaking SMTP, including standard extensions. Started out of dissatisfaction with existing mail servers, it aims to be a fairly complete, secure, and straightforward mail transfer agent. The software is released under the ISC license and is freely usable by everyone.

OpenSMTPD website preview

Live preview of opensmtpd.org via the WordPress mShots service — it can take a few seconds to generate on a first visit.

OpenSMTPD: strengths & things to check

Strengths

Completely free to use — this directory lists no paid plan for it.
Covers smtp, mail server, openbsd, open source — see the focus areas listed in its key facts.
Has 6 close alternatives in the same category on this page, so switching or comparing is easy.

Things to check

Free tools can change their model or shut down — avoid locking critical work into it without an export path.
Current plan prices are not listed here (they change too often to print reliably) — confirm the exact price on the official site.
It is one of 565 tools in the Communication & Collaboration category here — compare it against the alternatives below before you commit.

Derived from this listing's own data (pricing model, focus areas and category) — not a hands-on review score.

OpenSMTPD pricing

Pricing model	Free — listed in this directory as a free tool, with no paid plan required to use it.
Free access	Yes — fully free
Current plan prices	Listed on the official site — prices change, so this directory links out instead of printing a number that may already be stale.
Official site	opensmtpd.org

OpenSMTPD key facts

Category: Communication & Collaboration
Pricing: Free — listed in this directory as a free tool, with no paid plan required to use it.
Focus areas: smtp, mail server, openbsd, open source
Official site: opensmtpd.org

OpenSMTPD FAQ

How much does OpenSMTPD cost?

Free — listed in this directory as a free tool, with no paid plan required to use it. Current plans and prices are listed on the official site (opensmtpd.org).

What is OpenSMTPD used for?

Free SMTP server implementation from the OpenBSD project. Its focus areas in the Communication & Collaboration category: smtp, mail server, openbsd, open source.

Where can I try OpenSMTPD?

On its official site, opensmtpd.org — the Visit Official Site button above goes straight there.

OpenSMTPD vs alternatives

	OpenSMTPD	Postfix	chasquid	Courier Mail Server
Pricing	Free — listed in this directory as a free tool, with no paid plan required to use it.	Free — listed in this directory as a free tool, with no paid plan required to use it.	Free — listed in this directory as a free tool, with no paid plan required to use it.	Free — listed in this directory as a free tool, with no paid plan required to use it.
Focus areas	smtp, mail server, openbsd, open source	email, smtp, mail server, self hosted, open source	email, smtp, mail server, go	mail server, smtp, imap, self hosted
Official site	opensmtpd.org	postfix.org	blitiri.com.ar	courier-mta.org
Directory status	Listed	Listed	Listed	Listed

Side-by-side from each listing's own directory data. Full alternative cards are below.

About the Communication & Collaboration category

Chat, video meetings, and messaging apps that keep teams connected. The Communication & Collaboration category on Tools Hub currently lists 565 tools. Alongside OpenSMTPD, it includes diaspora*, Libervia, Hyphanet, GoToSocial.

FreeCommunication & Collaborationsmtpmail-serveropenbsdopen-source

Alternatives to OpenSMTPD

Tools in the same Communication & Collaboration category that share focus areas with OpenSMTPD — worth comparing before you commit:

Communication & Collaboration

Postfix

Fast, easy to administer, and secure mail server

Freeemailsmtpmail-serverself-hosted

Communication & Collaboration

chasquid

An SMTP server focused on simplicity, security and ease of operation

Freeemailsmtpmail-servergo

Communication & Collaboration

Courier Mail Server

Integrated mail and groupware server based on open protocols

Freemail-serversmtpimapself-hosted

Communication & Collaboration

Dovecot

The secure, high performance email server

Freemiumemailimapmail-serverself-hosted

Communication & Collaboration

EmailRelay

Lightweight SMTP store-and-forward mail server with POP access

Freeemailsmtpmail-serverself-hosted

Communication & Collaboration

Exim

The Exim Internet Mailer, a flexible message transfer agent

Freeemailmtasmtpmail-server

More in Communication & Collaboration

Comparing tools in the Communication & Collaboration category? These related listings are worth a look: diaspora* — Decentralized social network where you own your data; Libervia — All-in-one XMPP tool for messaging, blogging, file sharing, and events; Hyphanet — Peer-to-peer platform for censorship-resistant, anonymous communication.