Steps to take:
Delete entire Auto-complete list in Desktop App:
1. Click on File, then options
2. Click on Mail and scroll down till you see the “Send Messages” category, about half way down, and click on the Empty Auto-Complete List button.
3. Click "Yes" to confirm this action, then click "OK" to exit out of the options menu.
Delete individual email address in OWA and Desktop App.
- Create a new email in Outlook.
- In the "To" box, start typing the email address you are looking to delete.
- As soon as her complete email address appears as an auto populate, stop typing and move your cursor to the address and to the right of the email address box (see attached).
- You should see an "X" appear in the box. Click on the "X" to clear that email address from the cache.
5. You will need to type in the complete email address manually one more time in order for the correct address to be cached again. Subsequently, the email address will auto populate again.