Some few examples below provides a better insight to how this is done.
Sample: Loading mail content
<?php
$mailer = new Mailer;
... //other codes here
$mailer->content('mail.body', 'file'); // load as a file
$mailer->content('Here is a mail text'); // load as a string
The content() method sets a default mail body. It preferably applied
after setting up the mail's default configuration setup although it can be used to
as a modifier to a previously declared default body.