Outlook has a feature that suggests other users based on your interactions while using Outlook. When you type someone's name in the search bar, or send an email, there will be Basic suggestions and Expanded suggestions options. If you do not like this option of suggested people in Outlook, you can completely turn it off according to the instructions below.
How to turn off suggesters in Outlook
Step 1:
Open the Outlook application and then click on the gear icon in the top right corner of the interface.

Step 2:
Go to the next interface, we click on General then click on Privacy and data to adjust.

Step 3:
Looking at the next customization, in the Suggested people section , users will click on the Clear data and turn off setting to delete all suggested people data in Outlook and turn off this feature in Outlook.

Finally click Save below to save the settings.
In case the user wants to reuse the name suggestion feature in Outlook, just click Activate expanded contacts suggestions.