Introduction

Hedwig is a high-performance, minimalist SMTP server implemented in Rust. It provides a streamlined solution for receiving, queuing, and forwarding emails to destination SMTP servers.

Configuration is supported in TOML (default) and HUML formats.

What Hedwig is

  • A fast SMTP relay focused on receiving and forwarding mail.
  • A durable queue backed by the filesystem.
  • A clean TOML configuration surface for listeners, auth, and policy.

What Hedwig is not

  • A full mail server suite (no mailbox delivery, IMAP/POP, or user management).
  • A feature-heavy MTA; it stays intentionally small.

Key features

  • Fast and efficient processing with an async core.
  • Persistent queue for reliability across restarts.
  • Forward-only behavior focused on delivery.
  • DKIM, TLS, and SMTP authentication support.
  • Per-domain rate limiting to protect sender reputation.

Where to go next