Free SMTP Email Tester
Verify your SMTP mail server configuration by sending a real test email. Enter your server host, port, credentials, and a recipient address to instantly confirm everything is working.
Privacy: Your credentials are transmitted over HTTPS and used only for the duration of the SMTP connection. They are never stored or logged.
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Frequently Asked Questions
What is SMTP?
SMTP (Simple Mail Transfer Protocol) is the standard protocol for sending email. Mail servers and clients use SMTP to transmit messages between sender and recipient mail servers. The default ports are 25 (server-to-server), 587 (submission with STARTTLS), and 465 (SSL).
Why does my SMTP connection fail?
Common causes: wrong port or server address, firewall blocking the SMTP port, authentication credentials incorrect, SSL/TLS configuration mismatch, or the server requires a specific IP to be whitelisted. Check the server logs for the specific error code.
What are SMTP response codes?
2xx = success (250 = OK). 4xx = temporary failure (try again). 5xx = permanent failure (do not retry). Key codes: 421 (service unavailable), 450/451 (mailbox temporarily unavailable), 550 (mailbox not found), 554 (transaction failed).