SMTP Test Tool

See the exact SMTP conversation log to troubleshoot connection issues instantly.

SMTP Server

Port

Security

Username

Password

From Email

To Email

Why Use an SMTP Test Tool?

Understanding the “handshake” between your server and the recipient’s server is the key to solving email sending problems.

Diagnose & Verify

Diagnose Sending Errors

See the exact server conversation to find out why your emails aren’t sending. Instantly identify authentication issues, port blocks, or server rejections.

Verify New Credentials

Before plugging new SMTP settings into your app or plugin, confirm your server, port, username, and password are all correct in a safe, isolated environment.

Check Port & Security

Ensure your server is reachable on the correct port (like 587, 465, or 2525) and that your chosen security protocol (TLS, SSL, or None) is properly configured.

Test Provider Setups

Switching to SendGrid, Mailgun, or Amazon SES? Use this tool to get a detailed, raw log of your first connection attempt to ensure your setup is perfect.

Common SMTP Responses Explained

250 OK

This is the most common success code. You’ll see it after a successful connection, when the ‘FROM’ and ‘TO’ addresses are accepted, and when the email is queued.

535 Authentication Failed

This error means your username or password is incorrect. Check your credentials, make sure you’re using the right API key or password, and try again.

Connection Refused

This means the tool couldn’t reach your server. This is almost always a sign of an incorrect server address, a blocked port by your firewall, or the wrong port number.

STARTTLS Failed

This indicates a mismatch in security protocols. You might be trying a TLS connection on an SSL-only port (like 465) or vice versa. Check your port and security setting.

SMTP verified? Choose your next step.

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