Important, sending too many testing emails can block your IP address.

There is a protocol that is set in the server, linked with the mail functionalities that helps preventing unauthorised entry of the mails to the server. One of the principle acts as when too many test mails are sent from a server it considers it as a spam and it could harmful. When number of testing mails are sent from a IP. The IP gets blocked and blacklisted. Making the changes in the type of email can avoid these instance to happen.

If you send too many testing emails from a single IP address, then your IP address will be blocked in our HostingRaja server firewall and your Email will stop working.
So, you should test it ONLY few times. 
For example, If you are working on a contact form or login form, you may test the Email functionality many times in a day from the same IP address. When you test it multiple times, then your IP address will be blocked. 
If you want to test the email functionality, then there is a work around solution to this problem.
Change your file name and test it. For example, First use test.php and then use test1.php and then use test2.php
You can test using the same file name at least 30 times, after that your file and IP will be blocked, so you should keep changing your IP and file name for testing purpose.
For more assistance contact HostingRaja.