Test an SMTP server and see the entire conversation.
Connect to SendGrid, Mailgun, Amazon SES, GMass, or any SMTP server and watch the exact client/server exchange. It’s a fast way to diagnose authentication, TLS, connection, and sending problems.
Need help interpreting the result? Read the SMTP tester FAQ.
Choosing a provider? See the technical SMTP service review.
SMTP connection details
Diagnostic test
Running SMTP test
Connecting…
What this catches
See where the SMTP connection actually breaks.
Instead of guessing from a generic “couldn’t send” message, the transcript shows the server responses involved in connecting, authenticating, negotiating security, and sending.
Connection problems
Confirm the hostname and port actually accept an SMTP connection.
TLS / SSL problems
Try the exact security mode required by your SMTP provider.
Authentication failures
See the SMTP server’s response when the username, password, or auth method is rejected.
Sending failures
Inspect the conversation if the server accepts a connection but rejects the sender, recipient, or message.