If you respond it is through your email address. That is why I use a "disposable" email address when responding to inquiries (or inquiring about) items on CL. If it starts getting a lot of spam, I close it and get another. Not usually a big problem but worth the effort. Easy to set up an free email address and some will allow you to set an auto-forward so the email is forwarded to your regular account. That way, you don't have to keep checking the disposable account.