How do you unsend an email in Gmail after you've already hit send?

Gmail has Undo Send, but it is a short window, not a true recall. Right after you send, a 'Message sent, Undo' bar appears bottom-left. Click Undo and it pulls the email back to a draft. Extend the window: Settings > See all settings > General > Undo Send > set the cancellation period to 30 seconds (the max). After that closes, the email is genuinely gone.

The key is setting that window to 30 seconds ahead of time, because the default is only 5. Ten seconds like yours would already be too late on the default.

Unlike Outlook on a company server, Gmail has no recall-a-read-email feature. Once the undo window passes it has left Google's servers, so the 30-second buffer is all you get.

On the mobile app it is the same: a black Undo toast pops at the bottom for a few seconds after sending. You have to tap fast.