mdnotion

It works if I paste the code in instead of the
related_posts(array('template_file'=>'yarpp-template-email.php'));
lines, but I would rather have those files modularized if at all possible!

get_template_part('yarpp-template-email.php');
and
get_template('yarpp-template-email.php');
dont work either

Ok, so what I ended up just doing was this in my wp-config file:

// Enable Debug logging to the /wp-content/debug.log file
define(‘WP_DEBUG_LOG’, true);

// Disable display of errors and warnings
define(‘WP_DEBUG_DISPLAY’, false);

So, maybe these notices will be helpful to the plugin developers down the road. But, if anyone has this problem, this is how I fixed it.