A Possible Extension to Gmail's Undo Send Feature

Gmail introduced this really cool feature that many find useful. It allows you to undo the email that you sent by mistake. It is like allowing you to put the bullet back into gun after the shot has been fired. But the catch here is that you can undo a message only within a time window of 10 seconds of clicking on send. Gmail does not actually send the message but stores it on its servers for the first 10 seconds during which you have an option to reconsider the contents, recipients list etc.

A way to extend this functionality could be to allow a much longer time window for undoing the send. As long as the recipient is a gmail user and has not yet checked his mailbox (that includes access using POP3, IMAP or forwarding to a non-gmail address) I guess it is fair to allow the user to undo the message. No one has actually seen the message. It is between gmail and me. Neither the recipient nor the cool desktop/mobile apps have checked the inbox so what's the harm ... although it does encourage typing sloppy messages on the first go (but that is loosely equivalent to sloppy code being written due to better debugging tools available).

Though I agree it can be a convoluted and risky feature to implement correctly or for that matter explain to the users. But wouldn't it be cool to just drop a letter in the mail box of your friend while he/she is on vacation and pick it up before he/she gets back from vacation. What do you think?

Also imagine the prospect fooling the eavesdropper on the network that an email with the "contents" has been sent while actually undoing it later using a different network (that you know is not being sniffed).