SMTP Test
Our Free SMTP Test Tool lets you quickly check your mail server’s connection, authentication, and encryption settings, ensuring reliable email delivery for any domain.
About SMTP Test
SMTP Test Tool: Free Online Mail Server Diagnostic
Test and diagnose your SMTP mail server instantly. Verify connection, authentication, and encryption using HasheTools’ Free Online SMTP Test Tool, perfect for mail admins, developers, and IT professionals.
The SMTP Test Tool helps you analyze and troubleshoot your mail server’s configuration in seconds. It connects to your SMTP host and checks if it’s properly set up for sending and receiving emails. Whether you’re configuring a new server or fixing email delivery problems, this test provides instant, accurate results.
What Is SMTP?
SMTP (Simple Mail Transfer Protocol) is the standard communication method used to send emails across the Internet.
It typically operates on:
- Port 25: Default port (may be blocked by some ISPs)
- Port 465: Encrypted using SSL
- Port 587: Encrypted using TLS (recommended for modern email clients)
Popular SMTP services include Gmail (smtp.gmail.com), Microsoft 365 (smtp.office365.com), and self-hosted mail servers like Postfix or Exim.
Why Use the SMTP Test Tool?
Our free SMTP tester helps ensure your email system runs smoothly and securely. You can:
- Verify Server Availability: Check if your mail server is online and responding.
- Test Authentication: Confirm username, password, and login methods (PLAIN, LOGIN, CRAM-MD5).
- Check Encryption: Validate SSL, TLS, or STARTTLS configurations for secure mail transfer.
- Troubleshoot Issues: Detect relay errors, timeouts, and invalid responses instantly.
- Validate Email Deliverability: Ensure your domain can send and relay emails properly.
How to Use the SMTP Test Tool
Follow these simple steps to run an SMTP diagnostic:
- Visit the HasheTools SMTP Test Tool page.
- Enter your SMTP Host (e.g., smtp.gmail.com).
- Choose your Port (25, 465, or 587).
- Enable SSL/TLS encryption if applicable.
- Enter authentication details (if required).
- Click “Run Test” to start the connection and view server responses.
You’ll see a live conversation log showing SMTP response codes, connection results, and any authentication or encryption details.
Common SMTP Response Codes
| Code | Meaning |
| 220 | Service ready, connection successful |
| 250 | Action completed successfully |
| 354 | Start mail input - waiting for message data |
| 421 | Service not available - try again later |
| 450/550 | Mailbox unavailable or relay denied |
| 530 | Authentication required or failed |
Testing SMTP Encryption
To ensure your mail server supports encryption:
- Use Port 465 for SSL or Port 587 for STARTTLS.
- Verify that the SMTP banner includes 250-STARTTLS.
- Check the server’s TLS certificate for validity using our SMTP TLS Certificate Check.
Common SMTP Issues and Fixes
| Issue | Possible Cause | Solution |
| Connection Timeout | Blocked ports or firewall rules | Allow outbound connections on ports 25, 465, or 587 |
| Authentication Failed | Invalid credentials | Recheck username/password or enable “Allow less secure apps” |
| Relay Access Denied | Mail server not configured for your domain | Enable SMTP authentication |
| SSL Errors | Expired or invalid certificate | Renew or reinstall the SSL/TLS certificate |
Example SMTP Test Output
220 smtp.example.com ESMTP Postfix
250-smtp.example.com Hello [192.168.1.1]
250-STARTTLS
250 AUTH LOGIN PLAIN
This output confirms that the mail server is active, supports STARTTLS, and accepts authentication methods.
Test Your Mail Server Now
The HasheTools SMTP Test Tool makes diagnosing mail server issues simple and reliable.
Quickly verify authentication, encryption, and connection details, all from your browser.
Run your Free SMTP Test today to ensure your emails reach their destination without errors!
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Frequently Asked Questions About SMTP Test
1. What does SMTP stand for?
SMTP stands for Simple Mail Transfer Protocol. It’s the protocol used to send emails between mail servers.
2. What ports does SMTP use?
SMTP typically uses ports 25, 465 (SSL), and 587 (TLS). Port 587 is recommended for secure email transmission.
3. How can I test SMTP authentication?
Enter your username and password in the test fields and run the test. The tool verifies whether authentication succeeds or fails.
4. What’s the difference between SMTP, IMAP, and POP3?
SMTP is used for sending emails, while IMAP and POP3 are used for receiving emails.
5. Can I test third-party servers like Gmail or Office 365?
Yes! You can test Gmail, Outlook, or any custom mail server by entering its SMTP host and port details.