On Ethereum Stack Exchange, I recently proposed an edit to an answer. Since I don't have enough reputation there yet, that edit needed approval. My edit was approved two days later, and I got no email notification for that. That is something that definitely deserves an email notification, and that should be the default. I didn't even get an inbox notification actually.
You already get notified through the '+2' notification in your achievement inbox. Why is it important you get an email or inbox notification about it? It's not like you have to take an additional action after your edit is approved, right? (Instead, I'd appreciate a notification when a suggested edit of mine is rejected, but I digress.)
If you insist on being notified additionally after your edit is approved, I can suggest the Follow Post feature.
As a side remark: some users, including me suggest hundreds of edits every month. I would definitely get annoyed if I got an email every time a suggested edit of mine was approved. I do know we're the exception ...