For an > System Preferences, click Siri, click Siri Suggestions & Privacy, select Mail in the sidebar, then deselect the Show Siri Suggestions in App checkbox. If you change your mind later, select the checkbox.
Open Siri preferences for me
You can also add events and information to Calendar and Contacts by moving the pointer over a date, time, phone number, email address, or street address until an outline appears, then clicking the arrow to take an action.