PHP is a globally acknowledged web programming language that has been largely adopted by the web developers. The popularity of this web programming language can be measured with the results of the survey conducted by W3Techs wherein the findings showed that approximately 82% web servers use PHP.
Although Android SDK has been the serving as the backbone for the development of out-of-the-box applications, developers have always been keen finding innovative solutions for developing Android apps that can serve to the needs of a large majority of targeted audience.
If you are required to test the functionality of PHP mail in your projects, which is without having to use external mail server, you can try these steps which will allow you to send and open emails locally. I assume you are running XAMPP server on your computer, it should work fine with WampServer too without any configuration.
The Internet started as ARPANET, which was a project for the United States Department of Defense, the objective of the project was to connect sever sites of super computers, so if one was destroyed, the remain computers would still work. This project was successful, so other computer sites in universities, government departments, and large corporations began connecting to the network.