Link Mailchimp Does: https://mailchimp.com/help/add-the-forward-to-a-friend-link/

merge tag populates a link when the email is sent. When a contact clicks the Forward to a Friend link, they'll be taken to a form to enter their friend's details and a message. Then, the friend receives an email that includes a link to view the email in their browser.

Minimize the chances that your contacts will be unsubscribed by the people they forward to.

Email report will show how often your email was forwarded and how often those forwarded emails were opened.