How you respond to questions from your website visitors is ultimately at your discretion, but we recommend that you respond by respectfully letting them know that you recognized them because they opted into partner marketing, and that you are happy to unsubscribe them if they don't want to receive any marketing emails from you.
Here is an example of such a response:
Thank you for reaching out! We only recognize and contact visitors to our site if they have opted in to receiving partner marketing through our partner network. Of course, if you don't want to receive any emails from us we don't want to bother you and are happy to unsubscribe you from future marketing communications.