Solution: Deleting Sent Emails from Recepient's Mailbox

Open sent Items in MS Outlook

Open email that needs recalling

Click on

Other Actions --> Recall this message

• Select "Delete Unread copies of this message"  
• Tick "Tell me if recall succeeds or fails for each receipient"
• Press OK

After this, keep monitoring your mail box and you will see all the ones that have been recalled and also the ones that cannot be recalled.