SMTP Diagnostic Tools
Stop guessing why your application is failing to authenticate. Execute real-time, network-level TCP connections to discover supported server mechanisms (PLAIN, LOGIN), inspect raw Base64 payloads, and debug 535 Authentication errors with actual server responses and absolutely zero simulated data.
Is your application failing to authenticate? SMTP doesn't send passwords in plain text. Enter your credentials to discover supported server mechanisms, view exactly how your credentials are encoded into Base64, and test them live.
SMTP Authentication is often a black box. Developers use libraries that hide the protocol implementation. This tool exposes the raw mechanics so you can debug failed connections accurately.
EHLO response, we show you exactly which methods (PLAIN, LOGIN, CRAM-MD5) your server actually accepts.AUTH command if sent over an unencrypted connection. We ensure STARTTLS or Implicit SSL is negotiated first.535 Authentication failed or a 454 Temporary authentication failure? See the exact code and message returned by the server to diagnose bans or wrong passwords.AUTH PLAIN method, but will intelligently fallback or display payloads for the 2-step AUTH LOGIN method.QUIT command immediately after the authentication phase, ensuring your server's connection limits aren't triggered.Your feedback has been submitted successfully. We appreciate your help in improving our tools.