Open Outlook
Go to the Sent Items folder
Double-click the email you want to unsend
Click File
Click Info
Click Resend or Recall
Click Recall This Message
Choose Delete unread copies of this message or Delete unread copies and replace with a new message
Click OK
Check the option to tell you if the recall succeeds or fails for each recipient if needed
Click OK again
Use Undo Send in Outlook on the web if available
Go to Settings
Select Mail
Select Compose and reply
Set the Undo send delay
Save changes