Alternatively, if you're not using Composer, you can download PHPMailer as a zip file, (note that docs and examples are not included in the zip file), then copy the contents of the PHPMailer folder into one of the include_path directories specified in your PHP configuration and load each class file manually:

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'path/to/PHPMailer/src/Exception.php';
require 'path/to/PHPMailer/src/PHPMailer.php';
require 'path/to/PHPMailer/src/SMTP.php';
If you're not using the SMTP class explicitly (you're probably not), you don't need a use line for the SMTP class. Even if you're not using exceptions, you do still need to load the Exception class as it is used internally.

https://github.com/PHPMailer/PHPMailer