RustMail

A fast, self-hosted SMTP mail catcher for development and testing.
Capture outbound email, inspect it in a modern UI, and assert on it in CI.

Documentation · API Reference · Docker Hub

Quick Start

docker run -p 1025:1025 -p 8025:8025 smyile/rustmail:latest

Point your app's SMTP at localhost:1025, then open localhost:8025. Emails appear in real time.

Docker Compose

services:
  rustmail:
    image: smyile/rustmail:latest
    ports:
      - "1025:1025"
      - "8025:8025"
    volumes:
      - rustmail-data:/data
    restart: unless-stopped

volumes:
  rustmail-data:

Install

Homebrew

brew install rustmailapp/rustmail/rustmail

Arch Linux (AUR)

yay -S rustmail-bin

From Source

git clone https://github.com/rustmailapp/rustmail
cd rustmail && make build

Pre-built Binaries

Download from GitHub Releases — Linux (x86_64, aarch64, armv7 — glibc + musl), macOS (Intel + Apple Silicon), and multi-arch Docker images.

Features

Persistent storage	SQLite-backed, emails survive restarts. --ephemeral for CI.
Full-text search	FTS5 across subject, body, sender, and recipients.
Real-time UI	WebSocket push — new email appears instantly. Dark/light mode, keyboard shortcuts.
CI-native	REST assertion endpoints, CLI assert mode, and a first-party GitHub Action.
Single binary	Frontend embedded at compile time. ~7 MB, zero runtime dependencies.
Auth header display	Parses DKIM, SPF, DMARC, and ARC headers with color-coded status badges.
Webhooks	Fire-and-forget POST on every new message.
Email release	Forward captured emails to a real SMTP server.
Optional STARTTLS	Advertised on the normal SMTP port when both --smtp-tls-cert and --smtp-tls-key are configured.
Export	Download any email as EML or JSON.
Retention policies	Auto-purge by age (--retention) or count (--max-messages).
TUI	Optional terminal UI client for Neovim and headless workflows.

GitHub Action

- uses: rustmailapp/rustmail-action@v1

- run: npm test  # your app sends emails to localhost:1025

- uses: rustmailapp/rustmail-action@v1
  with:
    mode: assert
    assert-count: 1
    assert-subject: "Welcome"

CLI Assert Mode

Run as an ephemeral mail catcher that exits with a status code — for CI without the GitHub Action:

rustmail assert --min-count=2 --subject="Welcome" --timeout=30s

Configuration

Configure via CLI flags, RUSTMAIL_* environment variables, or a TOML config file:

rustmail serve --bind 0.0.0.0 --smtp-port 2525 --http-port 9025
rustmail serve --retention 24 --max-messages 1000
rustmail serve --webhook-url https://hooks.example.com/email
rustmail serve --smtp-tls-cert ./certs/localhost.pem --smtp-tls-key ./certs/localhost-key.pem

STARTTLS is optional and uses the same SMTP port via explicit upgrade. RustMail advertises STARTTLS only when both the certificate and private key are configured.

See the full configuration reference.

TUI

A terminal UI that connects to a running RustMail instance. Also available as a Neovim plugin.

Documentation

Full docs at docs.rustmail.app:

• Getting Started
• Docker
• Configuration
• CI Integration
• API Reference

License

Licensed under either of:

• MIT License
• Apache License, Version 2.0

at your option.