About Email Server Diagnostics (SMTP & STARTTLS)
What is this tool?
The Advanced Email Diagnostics tool performs a deep technical analysis of any mail server. It connects directly to the SMTP port (usually 25 or 587) to verify server responsiveness, supported commands (EHLO), and encryption capabilities (STARTTLS).
It also includes a Mail Banner Analyzer, which inspects the initial greeting sent by the server to identify potential information leaks (like exposing internal hostnames or software versions) that could be leveraged by attackers.
How to use
- SMTP Test: Verifies basic connectivity and lists supported authentication methods.
- STARTTLS: Checks if the server supports upgrading a plaintext connection to a secure TLS connection, and inspects the provided certificate.
- Mail Banner: Evaluates the server's greeting message against security best practices.
Why is it important?
Properly configured mail servers are essential for both deliverability and security.
- Prevent Eavesdropping: Without STARTTLS, emails are transmitted in plaintext, making them vulnerable to interception.
- Troubleshoot Routing: Identify exactly where an SMTP connection is failing (e.g., firewall block, misconfigured port, TLS handshake failure).
- Security Posture: Ensure your mail server isn't broadcasting sensitive version information to the public internet.