Open the sent email in Outlook
Select Message or File, depending on your Outlook version
Choose Actions
Select Recall This Message
Choose Delete unread copies of this message or Delete unread copies and replace with a new message
Select Tell me if recall succeeds or fails for each recipient if needed
Click OK
Note that recall works only if both you and the recipient use Microsoft Exchange or Microsoft 365 in the same organization
Note that recall usually does not work if the recipient has already opened the message
Use Undo Send in Outlook on the web or new Outlook if available
Open Settings
Go to Mail
Select Compose and reply
Set Undo send delay
Save changes
After sending, select Undo within the delay window