Change email message on Reply

Hi, I’m trying to get the right condition to change email message when there is a Reply, so Reply emails can be different from New messages just in email. I’ve tried this in class-fep-emails.php:

if ($post_status == fep_get_option(‘reply_post_status’) ) {
$message .= __(‘kdkekeke’, ‘front-end-pm’).”\r\n”;
}
But this is not working.. so, what should be the right condition or filter that I need to use to get this achieved?

Thank you in advance.

https://wordpress.org/plugins/front-end-pm/