I don’t think email notifications work correctly when posts are modified. (I’m set up to receive notification of all posts.) I’ve seen these two things happen:
I made a post, and got the notification. Then I modified the post and get a second notification with the original (pre-modification) text.
Someone made a post and I got the notification. Someone else posted a reply and I got the notification. The first user then modified his original post and I received a notification that included the text of the reply – not the text of the first post (the one that was modified).