Smart confirmation before sending mail

[EternityForest]

I think this could really be a "killer app" for just about any mail solution.

Almost everyone seems to have experienced sending mail to the wrong person, so this feature could be very helpful.

The way I imagine it, you could improve greatly on how Gmail's native app does it, by showing a summary of the text you're about to send, previews of any images, and the avatars of all receivers, to make things immediately obvious, similar to how there is a summary shown at an online checkout.

Going even further, you could later add some on-device machine learning that requires a second confirmation step to send anything predicted to be highly likely to be a mistake, either based on training from previous messages, or even a list of "Likely to be regretted" keywords(My password is, I really _$#&4$ing hate, etc).