If you are using Outlook desktop client, follow these steps:
- Select "Options" from the File menu.
- Select the "Mail" tab, and then click the "Editor Options" button.
- Click the "Advanced" tab, and then clear the check mark from "Show AutoComplete Suggestions."
- Click Ok
For Outlook on the web, follow these steps:
- At the top of the page, select Settings > View all Outlook settings > Mail > Compose and reply.
- Under Text predictions, clear the “Suggest words or phrases as I type” check box.