📧 SMTP Connection Tester
Diagnose email delivery issues in seconds. Test your SMTP server connectivity, verify authentication credentials, and send test payloads to any inbox.
Why Use an Online SMTP Tester?
Configuring email servers is one of the most frustrating parts of modern web development. Between firewall blocks, incorrect TLS versions, and "App Passwords," getting your application to send mail can take hours of trial and error.
Our SMTP Test Tool acts as a neutral third party. If our tool can connect to your server but your app can't, you know the issue lies in your code or local environment. If our tool also fails, the problem is likely with your SMTP provider or credentials.
Common SMTP Ports and When to Use Them
- Port 587 (TLS): This is the modern standard for mail submission. It uses opportunistic encryption (STARTTLS) and is supported by almost all providers like Gmail, SendGrid, and Mailgun.
- Port 465 (SSL): Known as "Implicit SSL," this port establishes a secure connection before any SMTP commands are sent. Use this if your provider specifically requires SSL over TLS.
- Port 2525: A non-standard port often used as an alternative to 587 when your ISP (Internet Service Provider) blocks standard mail ports.
- Port 25: The original SMTP port. It is mostly used for server-to-server communication and is frequently blocked on consumer and cloud networks to prevent spam bots.
Troubleshooting Connection Failures
If your connection fails, check for these common issues:
- App Passwords: Providers like Gmail and Outlook require you to generate a specific "App Password" if you have Two-Factor Authentication (2FA) enabled. Your normal login password will not work.
- Firewalls: Ensure your mail server allows connections from external IPs.
- Hostnames: Double-check that you aren't using a "Web" URL (like mail.google.com) instead of the actual SMTP endpoint (smtp.gmail.com).