You can give messages you send in Outlook an expiration date. Once the expiration date has been reached the message header is still visible in Outlook, it will however have a strikethrough. The email can still be opened and accessed but will give give the recipient the indication message is no longer relevant.

- Create a new email message

- In the Ribbon, goto Options on the Message tab.

- In the bottom right corner click the arrow pointing downward

- In the message options window under Delivery Options tick the expires after checkbox. Select the desired date and time.

- Now click Close