In this quick tutorial Arvind Bhardwaj shows a method for testing your scripts that need to send emails, but on your localhost system.

While developing web applications on localhost you must have always missed the functionality to send mails. As localhost does not support email service, so it has always been a bottleneck for email testing on localhost. But I have found a simple way to test emails on localhost using PHP. I have overridden the default mail() function of PHP to create a text/html file based on the email format. If the email is in html format, an HTML file is created otherwise a text file is created. You can see in this file what exactly is the content sent in your mail. See how does it work.

He shows how to override the mail function with your own custom "mail" function, just in a difference namespace. He includes the sample code to send the email (the "mail" function), a basic HTML template you can use and and example of it in use.