Microsoft has replaced the recall rule system with a built-in "Undo Send" timer.

Using  New Outlook for Windows or Outlook on the Web,

You need to recall a sent email. 

1. Click the Settings icon (the gear symbol) in the top-right corner of the window.
2. Select Mail from the left-hand column and click on Compose and reply.
3. Scroll down until you find the Undo send section.
4. Move the slider to select how long Outlook should pause before sending (up to 10 seconds).
5. Click Save at the bottom.
6. Whenever you hit send, a small "Undo" button will hover at the bottom of your screen for those 10 seconds. Clicking it stops the email and reopens your draft.