OpenSMTPD
opensmtpd.org
Spec sheet
- Purpose
- OpenSMTPD implements server-side SMTP and lets machines exchange email with systems that speak SMTP.Read 7 Oct 2026 · opensmtpd.org
- Platforms
- The portable release lists OpenBSD, FreeBSD, NetBSD, DragonFlyBSD, Linux, SmartOS, and macOS; support depends on package maintainers providing regular development feedback.Read 7 Oct 2026 · opensmtpd.org
- Security
- Project goals include careful validity checks on network input and privilege separation to mitigate possible security bugs.Read 7 Oct 2026 · opensmtpd.org
- Support
- The project is volunteer-developed and is not backed by a commercial entity.Read 7 Oct 2026 · opensmtpd.org
- License
- The project says the software is freely usable and reusable under an ISC license.Read 7 Oct 2026 · opensmtpd.org
- Delivery
- Supported delivery methods include LMTP, Maildir, mbox, mail delivery agent commands, and relaying to another SMTP server.Read 7 Oct 2026 · man.openbsd.org
- Filtering
- Mail filters can evaluate SMTP sessions at phases including connection, HELO/EHLO, sender, recipient, data, and commit.Read 7 Oct 2026 · man.openbsd.org
- Mail handling
- It accepts matching messages into a mail queue and dispatches them according to configured actions.Read 7 Oct 2026 · man.openbsd.org
- Packaging
- The portability team adds code for other operating systems but does not package OpenSMTPD for them.Read 7 Oct 2026 · opensmtpd.org
- Queue encryption
- The configuration supports encrypting queue files with AES-256-GCM.Read 7 Oct 2026 · man.openbsd.org
- Security reporting
- The project directs security issue reports to its private developers mailing list.Read 7 Oct 2026 · opensmtpd.org
- TLS
- Configuration supports STARTTLS and SMTPS for incoming connections, and TLS options for relaying mail.Read 7 Oct 2026 · man.openbsd.org
Plans and prices
OpenSMTPD Free FREE Server-side SMTP implementation; runs on supported Unix systems Read 7 Oct 2026 · opensmtpd.org
Where Specifiction places it
- Mail Server Software#28 of 347.4
