SMTP Tester Tool – User Guide

Purpose and Use Cases

This SMTP Tester is designed to help developers, system administrators, and IT professionals quickly test and validate their SMTP (Simple Mail Transfer Protocol) server configurations.

Primary Use Cases:

• Email Integration Testing: Verify SMTP settings before implementing email functionality in applications

• Troubleshooting: Diagnose email delivery issues and configuration problems

• Server Migration: Test new SMTP server configurations before going live

• Security Audits: Validate that email servers are properly configured and accessible

• Development: Test email functionality during application development

Key Benefits:

• Client-Side Security: All testing happens in your browser – credentials never leave your machine

• Instant Feedback: Get immediate results with detailed error messages

• No Installation Required: Works directly in any modern web browser

• Comprehensive Testing: Tests all aspects of SMTP configuration and authentication

Step-by-Step Usage Procedure

Step 1: Access the Tool

1. Save the HTML file to your computer

2. Open the file in any modern web browser (Chrome, Firefox, Safari, Edge)

3. The tool will load with a clean, professional interface

Step 2: Configure Server Settings

Section: Server Configuration

1. SMTP Host (Required)

   • Enter your SMTP server address

   • Examples: smtp.gmail.com, smtp.office365.com, mail.yourdomain.com

2. Port (Required)

   • Select the appropriate port from the dropdown

   • Common options:

     • 587 (Recommended) – Most modern SMTP servers

     • 465 – SSL/TLS encrypted connection

     • 25 – Standard SMTP port (often blocked by ISPs)

     • 2525 – Alternative port when 587 is blocked

3. Encryption (Required)

   • Choose the encryption method:

     • STARTTLS (Recommended) – Upgrades connection to TLS

     • SSL/TLS – Direct SSL connection

     • None – Unencrypted (not recommended)

Step 3: Enter Login Credentials

Section: Login Credentials

4. Username (Required)

   • Enter your full email address or SMTP username

   • Example: your.email@gmail.com or user@yourdomain.com

5. Password (Required)

   • Enter your SMTP password or app-specific password

   • For Gmail: Use an “App Password” if 2FA is enabled

   • The field is masked for security

Step 4: Set Up Test Email

Section: Test Email Details

6. From Address (Required)

   • Enter the sender email address

   • Must match your SMTP authentication username in most cases

7. To Address (Required)

   • Enter the recipient email address

   • Use your own email for testing to verify delivery

8. Subject (Required)

   • Enter a subject line for the test email

   • Default: “SMTP Test Email”

9. Message Body (Required)

   • Enter the content of your test email

   • Default text is provided

Step 5: Execute the Test

10. Test Connection

    • Click the blue “Test Connection” button

    • The button will show a loading spinner during testing

    • Wait for the process to complete (typically 10-30 seconds)

Step 6: Interpret Results

Success Scenario:

• Green success message appears

• Message: “Test Email Sent Successfully!”

• Includes timestamp of sending

• Check the recipient’s inbox for the test email

Failure Scenario:

• Red error message appears

• Detailed error description

• Common errors include:

  • “Invalid credentials” – Wrong username/password

  • “Could not connect to host” – Server unavailable or wrong host/port

  • “Authentication failed” – Login issues

  • “Connection timeout” – Network or firewall issues

Step 7: Troubleshooting (If Test Fails)

Common Issues and Solutions:

1. Authentication Failed

   • Verify username and password

   • For Gmail: Enable 2FA and use App Password

   • Check if the account requires “Less Secure App” access

2. Connection Timeout

   • Verify SMTP host address

   • Check if the port is correct and not blocked

   • Test with telnet: telnet smtp.host.com 587

3. Port Issues

   • Try alternative ports (587, 465, 2525)

   • Check firewall settings

   • Verify if your ISP blocks SMTP ports

4. Encryption Mismatch

   • Match encryption type with port:

     • Port 587 → STARTTLS

     • Port 465 → SSL/TLS

   • Try different encryption methods

Step 8: Clear and Retest

• Use the “Clear Fields” button to reset the form

• Make necessary adjustments based on error messages

• Retest with corrected settings

Security Notes

•  All processing happens in your browser – no server involvement

•  Credentials are not stored – they disappear when you close the page

•  No data is sent to third parties – only to your specified SMTP server

•  Use on trusted computers only – avoid public computers

•  Clear browser cache after testing if concerned about security

Example Configurations

Gmail Configuration:

SMTP Host: smtp.gmail.com
Port: 587
Encryption: STARTTLS
Username: your.email@gmail.com
Password: [App Password]
From: your.email@gmail.com
To: recipient@anydomain.com

Office 365 Configuration:

SMTP Host: smtp.office365.com
Port: 587
Encryption: STARTTLS
Username: your.email@yourdomain.com
Password: [Your Office 365 Password]
From: your.email@yourdomain.com
To: recipient@anydomain.com

Custom SMTP Server:

SMTP Host: mail.yourdomain.com
Port: 587
Encryption: STARTTLS
Username: your.email@yourdomain.com
Password: [Your Email Password]
From: your.email@yourdomain.com
To: recipient@anydomain.com

Best Practices

1. Start with common configurations (Port 587 + STARTTLS)

2. Use app-specific passwords for services with 2FA

3. Test with your own email address as recipient first

4. Keep the tool for future testing – bookmark or save locally

5. Clear fields after testing if using a shared computer

This tool provides a quick, secure way to validate SMTP configurations without installing additional software or exposing credentials to third-party services.