MailFang

MailFang is the email testing tool that you've been waiting for. It provides a local smtp server and a modern webui to view your emails.

Live Demo

About

Use MailFang locally during development, deploy it in a sandbox, or use it in your staging environment instead of sending emails to an external service. Regain control of your data and eliminate unnecessary costs.

Features

• Easy deployment via docker or single file binary
• View rendered email content, inspect headers, attachments and raw emails
• Preview emails in different viewports and block remote content loading
• Realtime updates in the webui
• ... and much more

Quickstart

docker run --name mailfang \
           -p 3000:3000 \
           -p 2525:2525 \
           -d cars10/mailfang

Open the webui on 0.0.0.0:3000 and send emails to 0.0.0.0:2525.

Usage

By default mailfang will use the following ports:

• Webui: 3000
• SMTP: 2525

Docker

Use the existing image from docker hub or from ghcr.io:

• cars10/mailfang
• ghcr.io/cars10/mailfang

docker run --name mailfang \
           -p 3000:3000 \
           -p 2525:2525 \
           cars10/mailfang

The services will be reachable via:

• Webui: 0.0.0.0:3000
• SMTP: 0.0.0.0:2525

Binary

1. Download the latest binary from the releases page
2. Set executable permissions: chmod +x ./mailfang-linux-amd64
3. Run MailFang: ./mailfang-linux-amd64

You can view all available configuration options by running ./mailfang-linux-amd64 --help.

Sending emails to MailFang

To send emails to Mailfang simply configure your email service to use the respective address and port where MailFang is running. Assuming you run MailFang in docker with default settings:

Rails ActionMailer

config.action_mailer.smtp_settings = {
  address:         "0.0.0.0",
  port:            2525,
  authentication:  "plain"
}

Swaks

You can do a simple test on the command line via swaks:

swaks --to recipient@example.com \
      --from sender@example.com \
      --server 0.0.0.0:2525 \
      --header "From: sender@example.com" \
      --header "To: recipient@example.com" \
      --header "Subject: Test Email" \
      --body "This is a plain text message."

Configuration

You can configure MailFang via command-line arguments or environment variables. When running in docker, environment variables are recommended.

Available Options

All configuration options are optional. The smtp server will accept all connections if no credentials are configured.

Option	Environment Variable	Description	Binary Default	Docker Default
--smtp-host	SMTP_HOST	SMTP server listen address	127.0.0.1:2525	0.0.0.0:2525
--smtp-username	SMTP_USERNAME	SMTP authentication username	none	none
--smtp-password	SMTP_PASSWORD	SMTP authentication password	none	none
--smtp-max-connections	SMTP_MAX_CONNECTIONS	Maximum number of concurrent SMTP connections	4	4
--web-host	WEB_HOST	Web server listen address	127.0.0.1:3000	0.0.0.0:3000
--database-url	DATABASE_URL	SQLite database URL	sqlite://./mailfang.db	sqlite:///data/mailfang.db

Configuration Example

Persistent storage with smtp authentication:

mkdir -p mailfang/data
docker run --name mailfang \
           -p 3000:3000 \
           -p 2525:2525 \
           -e SMTP_USERNAME=user \
           -e SMTP_PASSWORD=pass \
           -e SMTP_MAX_CONNECTIONS=10 \
           -e DATABASE_URL=sqlite:///data/mailfang.db \
           -v ./mailfang/data:/data \
           cars10/mailfang

Database Persistence

MailFang saves emails in a local sqlite database. To persist the data:

When running via docker mount a volume to /data.

The binary defaults to ./mailfang.db, change it by using --database-url sqlite:///path/to/mailfang.db or via environment variables DATABASE_URL=sqlite:///path/to/mailfang.db

SMTP Server

The SMTP server mostly implements RFC 5321 - Simple Mail Transfer Protocol.

It supports the following authorization methods:

• no auth
• PLAIN
• LOGIN
• CRAM-MD5

By default it accepts a maximum of 4 open connections at the same time. This is configurable via --smtp-max-connections 12 or SMTP_MAX_CONNECTIONS=12.

Development

Prerequisites

• Docker and Docker Compose
• Rust
• Node.js

Running

Run make dev to start the frontend and backend, access the frontend on http://localhost:5173.

Alternatives & Inspiration

MailFang is inspired partly by tools like:

• mailcatcher
• mailhog
• JSX Email

License

GNU GPL v3