Alternatives to OpenSMTPD
A free SMTP server from the OpenBSD project for sending and receiving email. The listings below can replace it for an important use case. Each note says what changes if you switch.
The original
OpenSMTPD
A free SMTP server from the OpenBSD project for sending and receiving email.
Replacements
Listings that take over the same core job as OpenSMTPD.
Postfix
A widely used open-source mail transfer agent for routing and delivering email.
Postfix is a widely used, security-focused MTA packaged by most operating systems with extensive documentation, though its configuration requires more mail server knowledge.
Exim
An open-source mail transfer agent for Unix systems with flexible routing and mail checking.
Exim is a GPL-licensed MTA with very flexible routing and extensive checks for incoming mail, but its configuration is more complex than OpenSMTPD's.
Mox
An all-in-one open-source mail server for low-maintenance self-hosted email.
Mox replaces the SMTP server and adds IMAP, webmail, automatic TLS and junk filtering in one program, though it is younger and less widely deployed.
Similar software
Related functionality, not a direct replacement.
Dovecot
An open-source IMAP and POP3 server that stores mailboxes and serves them to mail clients.
Cyrus IMAP
An open-source email, contacts and calendar server with IMAP, JMAP, CalDAV and CardDAV support.
Mailu
A full-featured self-hosted mail server delivered as a set of Docker images.
docker-mailserver
A complete mail server with SMTP, IMAP, antispam and antivirus, packaged as a single container.
Google Postmaster Tools
Google's web dashboard for checking a sending domain's reputation and mail deliverability to Gmail.
