Trigger Email when change/update existing post

I can’t figure out how it triggers the email to be sent, but assume its on any NEW post.

If you edit the post in any way (update) then re-post/republish, an email is not sent.

Say you have 100 users subscribe since the post went out, and you update to it, and have it re-deliver that post (with changes or updates) to all users.

I know that it might get annoying if it is edited 10 times they get 10 emails.

In that case, I know that would happen, and would save a draft until it is ready and they publish to post, and then want the email to be fired.

How can you have it email on updates?
I’d even go modify the back end code to trigger, if I knew where to look under the hood on how it checks for new posts then triggers.

It looks like the Author is MIA or abandoned this, but maybe someone else has looked at this.