How can Composer be used to install and manage PHP Mailer classes effectively for email functionality in PHP applications?

To install and manage PHP Mailer classes effectively for email functionality in PHP applications, Composer can be used to easily add the required dependencies to the project. By creating a `composer.json` file and specifying the PHP Mailer package as a dependency, Composer will automatically download and install the necessary files. This allows for seamless integration of PHP Mailer classes into the project without the need for manual file management.

```php
// composer.json
{
    "require": {
        "phpmailer/phpmailer": "^6.5"
    }
}
```

After creating the `composer.json` file with the specified PHP Mailer dependency, run `composer install` in the terminal to download and install the required files. This will make the PHP Mailer classes available for use in the PHP application, allowing for easy implementation of email functionality.