[leghifla]

You receive an email for your flight: tomorrow at 10am. When you arrive at the airport, you are told the flight has already departed.

"How is that possible, it is 9am and my flight is at 10am?"

"No sir, your flight was at 8am"

Checking your email, you see 8am and you have questions about your sanity

[_fat_santa]

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.

[macintux]

Exactly. Immutability has many virtues; this is the wrong direction.