Unlike Windows Server 2008 which includes the full IIS SMTP server component, Windows 7 doesn't natively support the same feature set. The IIS SMTP service was deliberately removed from client Windows versions after Windows XP. However, developers still need local email testing capabilities during application development.

Here are three practical approaches to implement SMTP functionality on Windows 7:

1. Using IIS SMTP Lite

While not identical to the Windows Server version, you can enable basic SMTP through IIS Manager:

1. Open "Turn Windows features on or off"
2. Navigate to: Internet Information Services > Web Management Tools > IIS 6 Management Compatibility
3. Check "IIS 6 Metabase Compatibility" and "IIS 6 WMI Compatibility"
4. Install hMailServer (third-party alternative)

2. Local SMTP Server with Papercut

For development testing, Papercut provides a lightweight SMTP server that captures outgoing emails:

// C# example sending test email
using (SmtpClient client = new SmtpClient("localhost", 25))
{
    client.Send(
        new MailMessage("test@local.dev", "recipient@test.com")
        {
            Subject = "SMTP Test",
            Body = "This email never leaves your machine"
        });
}

3. Dockerized SMTP Solution

For more advanced scenarios, consider running a containerized mail server:

docker run -p 25:25 -p 143:143 -e MAILNAME=test.dev -e SMTP_USER=user:password -d namshi/smtp

• Always bind to 127.0.0.1 to prevent accidental external delivery
• Configure your email client to use port 25 with no authentication
• Consider message queuing for batch email processing tests
• For ASP.NET applications, update Web.config:

<system.net>
  <mailSettings>
    <smtp deliveryMethod="Network" from="test@local.dev">
      <network host="localhost" port="25"/>
    </smtp>
  </mailSettings>
</system.net>

When testing email functionality locally:

• Implement email logging to verify content formatting
• Test both plain text and HTML email variants
• Simulate different SMTP response codes (250, 550, etc.)
• Validate attachment handling

Remember that these local solutions shouldn't be used in production. When deploying to live environments:

• Switch to proper SMTP credentials
• Implement TLS encryption
• Configure SPF/DKIM records if sending external emails
• Monitor email queue processing

Windows 7 doesn't include a built-in SMTP server component like Windows Server 2008 does. The IIS SMTP service was specifically designed for server operating systems and wasn't included in client versions of Windows. However, there are several workarounds for developers who need local SMTP capabilities for testing purposes.

One of the most popular free alternatives is hMailServer, which runs perfectly on Windows 7:

1. Download hMailServer from https://www.hmailserver.com/
2. Run the installer with default settings
3. During configuration:
   - Set up your domain (e.g., test.local)
   - Create an account for testing
   - Configure SMTP relayer if needed
4. Configure your application to use localhost:25

For quick testing without full server setup:

1. Download Papercut from https://github.com/ChangemakerStudios/Papercut
2. Extract and run Papercut.exe
3. It automatically listens on port 25
4. All sent emails will be displayed in the UI
5. No authentication needed for local testing

A specialized tool for development environments:

1. Install via Chocolatey: choco install smtp4dev
2. Runs as system tray application
3. Captures all outgoing mail
4. Provides REST API for automated testing
5. Supports multiple simultaneous connections

Here's sample C# code to test your SMTP setup:

using System.Net;
using System.Net.Mail;

var client = new SmtpClient("localhost", 25);
client.EnableSsl = false; // For local testing only

var message = new MailMessage("test@yourdomain.com", "recipient@example.com")
{
    Subject = "SMTP Test",
    Body = "This is a test email from your local SMTP server"
};

try 
{
    client.Send(message);
    Console.WriteLine("Email sent successfully");
}
catch (Exception ex)
{
    Console.WriteLine($"Error: {ex.Message}");
}

If you need to test from multiple devices:

• Configure your firewall to allow port 25
• Use your machine's IP instead of localhost
• Consider using a different port if your ISP blocks 25

Remember these solutions are for testing only. For production:

• Use proper SMTP services like SendGrid, Mailgun
• Implement proper authentication
• Set up SPF/DKIM records
• Monitor for abuse