Free Online SMTP Test Tool: Verify Email Server Configuration
Quickly diagnose email sending issues. Use our online SMTP checker to run a live connection test. We attempt a real-world mail submission to verify your SMTP host, port, and credentials in seconds.
How to Test Your SMTP Server Settings
If you are setting up a WordPress plugin, a CRM, or a custom application to send transactional emails, use this tool to confirm your SMTP settings are correct before deployment.
- SMTP Host: Enter your server address (e.g., smtp.gmail.com or mail.yourdomain.com).
- Port: Choose your SMTP port (Commonly 587 for TLS or 465 for SSL).
- Authentication: Enter the username and password provided by your email service provider.
- Security: Select your encryption type. Most modern servers use STARTTLS on port 587. Choose "Auto" to let our tool automatically detect the correct security protocol based on your port configuration.
- Test: Click "Run Test" to view the diagnostic log.
What is SMTP and Why Do You Need an SMTP Test Tool?
SMTP (Simple Mail Transfer Protocol) is the universal language servers use to send and relay emails across the internet. While it sounds simple, a single incorrect character in your configuration can lead to "silent" failures where emails are never sent. An online SMTP test tool is essential for:
- Developers: Debugging application code that isn't sending mail.
- IT Admins: Ensuring firewalls aren't blocking outgoing mail ports.
- SaaS Users: Verifying credentials for third-party platforms like SendGrid, Mailgun, or Amazon SES.
SMTP Ports: Which One Should You Use?
Choosing the right port is the #1 reason for connection timeouts. Use this Port information as a quick reference for your email server test.
- 587 (STARTTLS): Modern Standard. Use this for almost all mail submissions.
- 465 (Implicit SSL/TLS): Secure Alternative. Used by Gmail and many legacy systems.
- 2525 (STARTTLS): The Fallback. Use this if your ISP blocks port 587.
- 25 (None): Avoid. Usually blocked by cloud providers (AWS/GCP) to prevent spam.
Common SMTP Errors and How to Fix Them
When you test your SMTP server, our tool may return specific error codes. Here is what they mean:
- 535 Authentication Failed: Your username or password is incorrect. Note: For Gmail/Outlook, you often need an "App Password" rather than your main account password.
- Connection Timeout: This usually means your hosting provider or ISP is blocking the port (often Port 25 or 587). Try switching to Port 2525.
- 550 Relay Denied: The server recognizes you but doesn't have permission to send mail to that specific recipient. Check your "From" email address.