Using classic Outlook for Windows in business environments
If you have a version of Office which includes Copilot, you can turn it off completely via File > Options > Copilot. Note that if you are in an organization (business) environment, you may not be able to control that setting yourself.
Alternatively, maybe you are seeing suggested replies in Outlook. Instructions for turning those off can be found at https://support.microsoft.com/en-us/outlook/use-suggested-replies-in-outlook .