MS Outlook has taken this approach, IIRC - you can send a "message cancellation", which is actually just an e-mail with a special header. This, however, requires all the people in the conversation to cooperate, i.e. use Outlook.
Hilarity ensues when someone tries to pretend that a message never existed by cancelling an e-mail sent outside Outlook's garden. (The non-Outlook user will get both the original and the "previous message doesn't exist, okay? Wink wink, nudge nudge" message.)
Hilarity ensues when someone tries to pretend that a message never existed by cancelling an e-mail sent outside Outlook's garden. (The non-Outlook user will get both the original and the "previous message doesn't exist, okay? Wink wink, nudge nudge" message.)