- In Outlook, click File > Options.
- Select Mail.
- Scroll roughly halfway down until you see Send messages. Ensure the Use AutoComplete List to suggest names when typing in the To, Cc, and Bcc lines box is checked.
- If it's already turned on, your first troubleshooting step should be to clear out the Auto-Complete list. Click the Empty AutoComplete List button.
- You'll see a confirmation window about clearing the AutoComplete list, Click Yes.
- Try sending a few test emails to the same email address.