Posthorn, self-hosted mail gateway

In plain words

Posthorn is a self-hosted email gateway that runs as a single Docker container or Go binary, allowing applications on a VPS to send mail through a transactional email provider. It sits between self-hosted apps and external email services, bypassing common SMTP port restrictions imposed by VPS providers. Users configure Posthorn once and point their applications to it for email delivery. The tool is designed for developers running multiple self-hosted services like Ghost, Gitea, or contact forms who need reliable email functionality without managing complex mail server configurations.

written from the facts on this page · September 2026

From the sources

Self-hosted email gateway between your apps and a transactional mail provider (Postmark, Resend, Mailgun, AWS SES, or outbound-SMTP). Three ingress shapes (HTTP form, HTTP API, SMTP). One Docker container, one TOML config. - craigmccaskill/posthorn

In the maker’s words, at launch

Introducing Posthorn, a self hosted email gateway. One docker container (or Go binary) between every self hosted app on your VPS and your transactional email provider. Set up Posthorn once, point your apps to it, done. I was trying to deploy Ghost on a DigitalOcean droplet and found that DO and many different VPS…

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