chasquid

chasquid is an SMTP server written in Go that aims to be simple to configure and hard to mis‑configure. It functions as a full‑featured mail transfer agent suitable for replacing traditional MTAs such as Postfix or Exim, targeting individuals and small groups. The server includes an HTTP monitoring endpoint that exports variables and tracing information for debugging, and it integrates smoothly with Debian, Ubuntu, and Arch Linux distributions.

The software supports multiple virtual domains, per‑domain users and aliases, and suffix‑dropping (user+tag@domain → user@domain). It can authenticate against Dovecot and provides hooks for greylisting, anti‑virus, anti‑spam, DKIM, and DMARC. Internationalized usernames (SMTPUTF8) and domain names (IDNA) are handled, and TLS is managed per domain with automatic Let’s Encrypt support, SPF, and MTA‑STS checks.

chasquid is released under the Apache‑2.0 license, is self‑hostable, free‑tier, and has no subscription model. Its documentation includes installation and how‑to guides, and the project welcomes contributions via its mailing list, GitHub repository, and IRC channel.