Well, I installed the MantisBT correctly without any problem on my local computer, I already changed the admin’s password and removed the admin folder in the directory. After this I signed up for a new account, there was a confirmation message flashed saying that I need to verify my registration via email. My problem here is that no verification message was sent to my email. According to one of the tutorials I found, I need to configure first my config_defaults_inc.php as the following. 

After complete the requirement of mail server, you have to make sure that Mantis use phpmailer to deal with send mail operation.
Phpmailer need openssl surport. So you must enable php_openssl extension in php configuration.

if you are using warmSever , you have go to warmServer ->PHP-> PHP extensions then click on the php_openssl