I suggest you look into getting composer
. https://getcomposer.org
Composer makes getting third-party libraries a LOT easier and using a single autoloader for all of them. It also standardizes on where all your dependencies are located, along with some automatization capabilities.
Download https://getcomposer.org/composer.phar to C:\Inetpub\wwwroot\php
Delete your C:\Inetpub\wwwroot\php\PHPMailer\
directory.
Use composer.phar
to get the phpmailer package using the command line to execute
cd C:\Inetpub\wwwroot\php
php composer.phar require phpmailer/phpmailer
After it is finished it will create a C:\Inetpub\wwwroot\php\vendor
directory along with all of the phpmailer files and generate an autoloader.
Next in your main project configuration file you need to include the autoload file.
require_once 'C:\Inetpub\wwwroot\php\vendor\autoload.php';
The vendor\autoload.php
will include the information for you to use $mail = new \PHPMailer;
Additional information on the PHPMailer package can be found at https://packagist.org/packages/phpmailer/phpmailer