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SMTP Server with Web Management Frontend

A comprehensive SMTP server with an integrated Flask-based web management interface. This application provides both a fully functional SMTP server and a modern web interface for managing domains, users, DKIM keys, and server settings.

Features

SMTP Server

  • Full SMTP Server: Send and receive emails with authentication
  • DKIM Support: Automatic DKIM key generation and email signing
  • TLS/SSL Encryption: Secure email transmission
  • Domain Management: Support for multiple domains
  • User Authentication: Per-user and per-domain authentication
  • IP Whitelisting: Allow specific IPs to send without authentication
  • Email Relay: Forward emails to external servers
  • Comprehensive Logging: Track all email and authentication activities

Web Management Interface

  • Modern Dark UI: Bootstrap-based responsive interface
  • Domain Management: Add, configure, and manage email domains
  • User Management: Create and manage email users with permissions
  • DKIM Management: Generate keys, view DNS records, verify setup
  • IP Whitelist Management: Configure IP-based access controls
  • Server Settings: Web-based configuration management
  • Real-time Logs: View email and authentication logs with filtering
  • DNS Verification: Built-in DNS record checking for DKIM and SPF
  • Health Monitoring: Server status and performance metrics

Quick Start

Prerequisites

  • Python 3.9 or higher
  • Linux/macOS (Windows with WSL)

Installation

  1. Clone or navigate to the project directory:

    cd /home/nahaku/Documents/Projects/SMTP_Server

  2. Run the setup script:

    chmod +x email_frontend/setup.sh
./email_frontend/setup.sh

  3. Initialize sample data (optional):

    .venv/bin/python app.py --init-data

  4. Start the unified application:

    .venv/bin/python app.py

The application will start both the SMTP server and web interface:

Usage Modes

Unified Mode (Default)

Run both SMTP server and web interface together:

.venv/bin/python app.py

SMTP Server Only

Run only the SMTP server without web interface:

.venv/bin/python app.py --smtp-only

Web Frontend Only

Run only the web management interface:

.venv/bin/python app.py --web-only

Development Mode

Enable debug mode with auto-reload:

.venv/bin/python app.py --debug

Custom Host and Port

Specify custom web server settings:

.venv/bin/python app.py --host 0.0.0.0 --port 8080

Configuration

Main Configuration File: settings.ini

The server uses a comprehensive configuration file with the following sections:

Server Settings

[Server]
SMTP_PORT = 25
SMTP_TLS_PORT = 587
hostname = your-domain.com
BIND_IP = 0.0.0.0
helo_hostname = your-domain.com

Database Settings

[Database]
database_path = email_server/server_data/smtp_server.db

TLS/SSL Settings

[TLS]
enable_tls = true
cert_file = email_server/ssl_certs/server.crt
key_file = email_server/ssl_certs/server.key

DKIM Settings

[DKIM]
enable_dkim = true
default_selector = default
key_size = 2048

Web Interface Configuration

The web interface can be configured through the settings page or by editing settings.ini. Changes require a server restart to take effect.

Web Interface Features

Dashboard

  • Server status overview
  • Domain, user, and DKIM key counts
  • Recent email and authentication activity
  • Quick access to all management functions

Domain Management

  • Add and remove email domains
  • Enable/disable domains
  • Automatic DKIM key generation
  • Domain-specific settings

User Management

  • Create email users with passwords
  • Assign users to domains
  • Set user permissions (regular user vs domain admin)
  • Manage user access levels

DKIM Management

  • View and generate DKIM keys
  • DNS record display with copy-to-clipboard
  • Real-time DNS verification
  • SPF record recommendations
  • Selector management

IP Whitelist Management

  • Add IP addresses or ranges
  • Domain-specific whitelisting
  • Current IP detection
  • Use case documentation

Server Settings

  • Web-based configuration editor
  • All settings sections accessible
  • Form validation and help text
  • Export/import configuration

Logs and Monitoring

  • Real-time email logs
  • Authentication logs
  • Filtering and pagination
  • Auto-refresh functionality
  • Error details and troubleshooting

API Endpoints

The web interface provides REST API endpoints for integration:

Health Check

GET /health

Returns server health status and basic information.

Server Status

GET /api/server/status

Returns detailed server status including SMTP server state, database counts, and configuration.

Server Restart

POST /api/server/restart

Restarts the SMTP server component.

Database Schema

The application uses SQLite with the following main tables:

  • domains: Email domain configuration
  • users: User accounts and authentication
  • whitelisted_ips: IP-based access control
  • dkim_keys: DKIM signing keys
  • email_logs: Email transaction records
  • auth_logs: Authentication attempts
  • custom_headers: Custom email headers

Security Features

Authentication

  • User-based authentication for email sending
  • Domain-specific user management
  • IP-based whitelisting
  • Secure password hashing

Email Security

  • DKIM signing for email authentication
  • SPF record support and verification
  • TLS encryption for secure transmission
  • DNS record validation

Web Interface Security

  • Session management
  • CSRF protection
  • Input validation and sanitization
  • Secure configuration handling

DNS Configuration

Required DNS Records

For each domain, configure the following DNS records:

DKIM Record

default._domainkey.yourdomain.com. IN TXT "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY"

SPF Record

yourdomain.com. IN TXT "v=spf1 ip4:YOUR_SERVER_IP ~all"

MX Record

yourdomain.com. IN MX 10 your-server.com.

The web interface provides the exact DNS records needed and can verify their configuration.

Troubleshooting

Common Issues

Port Permission Issues

If you get permission denied errors on ports 25 or 587:

sudo setcap 'cap_net_bind_service=+ep' .venv/bin/python

Database Issues

Reset the database:

rm email_server/server_data/smtp_server.db
.venv/bin/python app.py --init-data

SSL Certificate Issues

Generate new self-signed certificates:

.venv/bin/python -c "from email_server.tls_utils import generate_self_signed_cert; generate_self_signed_cert()"

DNS Verification Fails

  • Ensure DNS records are properly configured
  • Wait for DNS propagation (up to 24 hours)
  • Check with online DNS checkers
  • Verify your domain's nameservers

Log Files

Check logs for detailed error information:

  • Application logs: Console output or systemd logs
  • Email logs: Available in web interface
  • Authentication logs: Available in web interface

Web Interface Issues

If the web interface is not accessible:

  1. Check that Flask is running on the correct host/port
  2. Verify firewall settings
  3. Check browser console for JavaScript errors
  4. Review Flask application logs

Development

Project Structure

├── app.py                      # Unified application entry point
├── main.py                     # SMTP server only entry point
├── settings.ini                # Configuration file
├── requirements.txt            # Python dependencies
├── email_server/               # SMTP server implementation
│   ├── models.py              # Database models
│   ├── smtp_handler.py        # SMTP protocol handling
│   ├── dkim_manager.py        # DKIM key management
│   ├── settings_loader.py     # Configuration loader
│   └── ...
├── email_frontend/             # Web management interface
│   ├── blueprint.py           # Flask Blueprint
│   ├── templates/             # HTML templates
│   ├── static/               # CSS/JS assets
│   └── ...
└── tests/                     # Test files

Adding Features

To add new features to the web interface:

  1. Add routes to email_frontend/blueprint.py
  2. Create templates in email_frontend/templates/
  3. Add static assets in email_frontend/static/
  4. Update navigation in sidebar_email.html

Testing

Run tests manually:

cd tests
./custom_test.sh

Send test emails:

.venv/bin/python tests/send_email.py

Production Deployment

Systemd Service

Create a systemd service for production deployment:

[Unit]
Description=SMTP Server with Web Management
After=network.target

[Service]
Type=simple
User=smtp-user
WorkingDirectory=/path/to/SMTP_Server
ExecStart=/path/to/SMTP_Server/.venv/bin/python app.py --host 0.0.0.0
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

Reverse Proxy

For production web interface, use nginx or Apache as a reverse proxy:

server {
    listen 80;
    server_name your-domain.com;
    
    location / {
        proxy_pass http://127.0.0.1:5000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

Security Considerations

  1. Change default secrets in configuration
  2. Use proper SSL certificates for web interface
  3. Configure firewall to restrict access
  4. Regular backups of database and configuration
  5. Monitor logs for suspicious activity
  6. Keep dependencies updated

Support

For issues and questions:

  1. Check the troubleshooting section above
  2. Review log files for error details
  3. Verify DNS and network configuration
  4. Test with sample data using --init-data

License

This project is licensed under the MIT License. See the LICENSE file for details.

Contributing

Contributions are welcome! Please:

  1. Follow the existing code style
  2. Add tests for new features
  3. Update documentation
  4. Submit pull requests for review

Note: This application is designed for educational and development purposes. For production use, ensure proper security configuration, monitoring, and maintenance.