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No you cannot, it is not part of the email protocol.

Once it is sent, it is gone.

I always have fun with those "Please delete messages" from Outlook sent to my email client.

Gmail does not literally unsend SMTP messages. To give you time to undo, Gmail delays sending the message for a few seconds. So if you don't select "Undo" within the time limit, your message will be sent.

How to use: https://support.google.com/mail/answer/1284885?hl=en

Note these instructions are for how to enable this on Gmail, the original. Inbox does this by default.

Yes, that was a nice strong statement but you are wrong, and the other guy is right. When you send a message from Inbox, you can cancel it, for a few seconds. It doesn't bother actually sending it until the Undo button has disappeared.

The statement I was replying to never mentioned pressing undo button within a specified interval.

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