Send Email If is a WordPress Plugin that ends an Email if specific conditions are met, to specific receivers.
The receiver of the Email can be stored in an Email Address Field on each post.
The Metabox for this is already provided by Send Email If on native WordPress posts.
Raw code must be edited to amend the conditions by which the Emails are sent, or to change the data sent in the email.
You can read more on its basic usage Document here
Currently you can download the plugin on GitHub