The desktop version of Outlook doesn’t have a simple undo send feature, but you can set a rule to delay every message you send. From the File tab, click Manage Rules & Alerts, then New Rule. Choose Apply rule on messages I send, then click Next twice, and Yes to confirm. You’ll reach a dialog box where you can click Defer delivery by a number of minutes. Check the box next to this rule, then click the link underneath to set how many minutes the delay should be—you can go from one to 120. Click through the wizard’s remaining screens to set the rule.