Popular email services offer undo send features. GmailPhone: In Google’s Gmail iOS app, the setting is turned on by default. On the website, click the gear icon in the right corner, select Settings, scroll down and click Enable Undo Send. When you send a message, you’ll see the Undo button at the top of the window. Web: Go to Outlook.com, click the Gear icon in the upper right, select Options then go down to Undo Send.

Source: Wall Street Journal January 27, 2017 19:27 UTC