GoGraphSMTP

A lightweight SMTP server implemented in Go that forwards emails via the Microsoft Graph API.

Features

• Supports both plain text and HTML emails.
• Handles email attachments.
• Logs all activities to a specified log file.

Configuration

The server requires a configuration file in YAML format. Below is an example GoSMTP.yaml:

azure:
  client_id: "your-client-id"
  client_secret: "your-client-secret"
  tenant_id: "your-tenant-id"

smtp:
  address: ":25"
  domain: "localhost"

log_file: "/path/to/log/file.log"

Setup

1. Build the Project

1. Clone the repository:

   git clone <repository_url>
   cd smtp_graph_project

2. Install dependencies:

   go mod tidy

3. Build the project:

   go build -o GoGraphSMTP main.go

2. Deploy as a Systemd Service

Service File Configuration

Create a systemd service file gographsmtp.service with the following content:

[Unit]
Description=GoGraphSmtp SMTP to Graph API Bridge
After=network.target

[Service]
Type=simple
User=root
ExecStart=/usr/local/bin/GoGraphSMTP
Restart=always
RestartSec=10
WorkingDirectory=/etc/GoGraphSMTP

[Install]
WantedBy=multi-user.target

Deployment Steps

Follow these steps to deploy the service:

1. Copy the binary file:

   cp GoGraphSMTP /usr/local/bin/

2. Create a directory for configuration:

   mkdir -p /etc/GoGraphSMTP

3. Copy the configuration file:

   cp GoSMTP.yaml /etc/GoGraphSMTP/

4. Copy the systemd service file:

   cp gographsmtp.service /etc/systemd/system/

5. Reload the systemd configuration:

   systemctl daemon-reload

6. Start the service:

   systemctl start gographsmtp

7. Enable the service to start on boot:

   systemctl enable gographsmtp

8. Check the service status:

   systemctl status gographsmtp

3. Managing the Service

Use the following commands to manage the service:

• Stop the service:

  systemctl stop gographsmtp

• Restart the service:

  systemctl restart gographsmtp

• View service logs:

  journalctl -u gographsmtp

Testing

1. Create a test PHP script or use any SMTP client to test the service.
2. Verify logs in the file specified in the log_file configuration or with journalctl.

Notes

• Ensure that your Azure app has the Mail.Send permission.
• Test the service with a sample email to confirm proper configuration.

License

MIT License