I could see this being useful for emails that send out coupon codes. If a coupon code is updated for some reason, that update can be pushed to the user without

I could see this being useful for emails that send out coupon codes. If a coupon code is updated for some reason, that update can be pushed to the user without having to send them another email. The problem is cases of where you would want to update an email after it is sent is few and far between.