What is docker-smtp?

docker-smtp is a minimal Docker image maintained by Bytemark Hosting that provides an Exim4 SMTP server for containerized applications to send outgoing email. It can operate in two modes: as a direct delivery SMTP server sending mail straight to recipients, or as a smart host that authenticates and relays through an external SMTP provider such as Gmail or SendGrid. The image exposes port 25 and is configured via environment variables including MAILNAME, RELAY_HOST, RELAY_PORT, RELAY_USERNAME, RELAY_PASSWORD, and RELAY_NETS. It runs on any architecture with the Debian exim4-daemon-light package. The project has not been updated since 2018 and uses Debian Stretch as its base.

Should you self-host docker-smtp?

docker-smtp scores 38/100 on selfhost.directory (how scoring works) and ranks #88 of 106 in Email. It has 145 GitHub stars.

There was no stable release in the past 12 months, so check the repository's recent activity before you rely on it.

Setup is easy: most people get it running in one sitting. An official Docker image is available. It is written mostly in Shell.

Its closest alternative on selfhost.directory is Listmonk (80/100, 24 017 stars). It scores higher overall, so compare the two before you pick. See docker-smtp vs Listmonk side by side.