Open Outlook and go to the Sent Items folder
Double-click the sent email to open it
Select File
Select Info
Choose Resend or Recall
Click Recall This Message
Select Delete unread copies of this message
Optionally select Tell me if recall succeeds or fails for each recipient
Click OK
Note that recall works only if both you and the recipient use Microsoft Exchange or Microsoft 365 in the same organization
If recall is not available, delete the email from Sent Items only on your account
If you want to prevent future sending, use Undo Send if enabled in Outlook settings