This article describes several ways to find someone's email address without using an email address lookup function.
Everyone needs an email address to create an account on social media sites like Facebook, Instagram, and LinkedIn. So you may be able to search the person's account for an email address.
Visit each of these social media platforms, plus any others you know or suspect the person uses, and search for them by name, age, school, company, hometown, or other information you know about them.
Even though the profile page is not public, sometimes people still make their email address visible so that someone who is not a friend or follower can contact them.