Simple SMTP Client

A simple and to the point SMTP test client

Built with .NET 10 - Modern, fast, and secure!

Download the release under the "release" tab.
Supports Basic Authentication to SMTP server.
Supports Anonymous connection to SMTP Server.
Supports TLS/SSL encryption with modern MailKit library:
- TLS 1.0, TLS 1.1, TLS 1.2, and TLS 1.3 (automatically negotiated)
- Auto/System Default mode for automatic protocol negotiation
- Secure by default with TLS 1.2+ recommended
- Works with SMTP servers in STARTTLS mode only. Does not support connecting to SMTP/SSL, SMTP over SSL, or SMTPS server on default port 465.
Runs on Windows (requires .NET 10 Runtime or later).
Modern async/await implementation for better performance and responsiveness.
Input validation for all required fields with helpful error messages.
Configurable connection timeout (5-300 seconds) with ability to cancel ongoing operations.
Save/Load settings - Your SMTP server configuration is automatically saved and restored between sessions.
Logging feature - All connection attempts, successes, and failures are logged to daily log files:
- View logs directly in the application
- Open log folder in File Explorer
- Automatic cleanup of logs older than 30 days
- Toggle logging on/off as needed

Settings and logs are stored in:

Windows: %LOCALAPPDATA%\SimpleSmtpClient\
- settings.json - Application settings
- Logs\ - Daily log files

Note: Passwords are never saved to disk for security reasons.