SMTP Server Tester & Verification
GMass-style SMTP tester with real-time protocol handshake logs, TLS/SSL ciphers, authentication checks, and email delivery verification. Settings automatically save for continuous multi-testing.
SMTP Server Configuration
Ready to verify SMTP server.
Fill in your host details on the left and click "Test SMTP Server". All raw protocol lines will appear here in real time.
Port 587 vs 465 vs 25
Port 587: Standard email submission port using STARTTLS. Recommended for almost all modern email services.
Port 465: Implicit SSL/TLS connection from byte 0.
Port 25: Server-to-server relaying, often blocked by residential ISPs.
Gmail App Password Required
Google no longer permits primary Google account passwords for SMTP. You must enable 2-Step Verification in your Google Account security settings, generate a 16-character App Password, and use that as the password.
Safe & Client-Side Stored
Your SMTP credentials are saved strictly in your local browser’s localStorage for convenience across tests. They are never stored on our servers or logged into databases.