Shortcode usage in email

I’m trying to send an email that contains a custom shortcode. The shortcode isn’t being parsed and the email sent contains the exact text entered in the message textbox. I found a default setting in email-user.php “mailuser_shortcode_processing” that is default false which I changed to true but the behavior is unchanged.

Do I need to change something else or could it be the custom shortcode? I assumed since the shortcode was added using add_shortcode it should be available to this plugin.

https://ww.wp.xz.cn/plugins/email-users/