LocalSMTP

A lightweight SMTP capture server for local development and testing. Catch all outgoing emails from your application without sending them to real recipients.

Features

• SMTP Server - Captures all emails on port 2025
• Web Interface - Modern React UI to browse captured emails
• Email-only Login - No passwords, just enter any email address
• Per-user Views - Inbox and sent views based on your login email
• Real-time Updates - Live email notifications via Server-Sent Events
• Attachments - Full support for email attachments
• Search - Find emails by subject, sender, or recipient
• SQLite Storage - Lightweight persistence (or in-memory mode)
• Single Binary - No external dependencies, easy deployment
• Docker Ready - Multi-arch images for amd64 and arm64

Installation

Docker (Recommended)

docker run -d \
  --name localsmtp \
  -p 3025:3025 \
  -p 2025:2025 \
  -v localsmtp-data:/data \
  -e DB_PATH=/data/localsmtp.db \
  -e AUTH_SECRET=your-secret-here \
  razzkumar/localsmtp:latest

Binary Release

Download the latest release from the Releases page.

# Linux/macOS
chmod +x localsmtp
./localsmtp

# Windows
localsmtp.exe

From Source

Requires Go 1.25+ and Node.js 18+.

# Clone the repository
git clone https://github.com/razzkumar/localsmtp.git
cd localsmtp

# Build the web UI
cd web
npm install
npm run build
cd ..

# Run the server
go run ./cmd/localsmtp

Usage

1. Start LocalSMTP using one of the methods above
2. Open http://localhost:3025 in your browser
3. Log in with any email address (e.g., dev@example.com)
4. Configure your application to use localhost:2025 as the SMTP server
5. Send test emails - they'll appear in your LocalSMTP inbox

Configuration

LocalSMTP is configured via environment variables. Create a .env file or set them directly.

Variable	Default	Description
HTTP_PORT	3025	Web interface port
SMTP_PORT	2025	SMTP server port
DB_PATH	(empty)	SQLite database path. Empty = in-memory (no persistence)
AUTH_SECRET	(empty)	Secret for signing session cookies. Set this in production

Example: Send Test Email

package main

import (
    "net/smtp"
)

func main() {
    from := "sender@example.com"
    to := "recipient@example.com"
    subject := "Test Email"
    body := "Hello from LocalSMTP!"

    msg := []byte("From: " + from + "\r\n" +
        "To: " + to + "\r\n" +
        "Subject: " + subject + "\r\n\r\n" +
        body + "\r\n")

    smtp.SendMail("localhost:2025", nil, from, []string{to}, msg)
}

Docker Compose

version: "3.8"
services:
  localsmtp:
    image: razzkumar/localsmtp:latest
    ports:
      - "3025:3025"
      - "2025:2025"
    volumes:
      - localsmtp-data:/data
    environment:
      - DB_PATH=/data/localsmtp.db
      - AUTH_SECRET=change-me-in-production

volumes:
  localsmtp-data:

Development

Prerequisites

• Go 1.25+
• Node.js 18+
• npm

Running in Development

# Terminal 1: Start the backend with hot reload (requires air)
air

# Terminal 2: Start the frontend dev server
cd web
npm run dev

Building

# Build web assets
cd web && npm run build && cd ..

# Build the binary
go build -o localsmtp ./cmd/localsmtp

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

License

MIT License - see LICENSE for details.