Confirmed Opt-In describes a situation where an organization or company with verifiably confirmed permission for a recipient’s email address to be added to their mailing list. Once the user submits an email to join a mailing list, the organization or company sends a confirmation email to ask the recipient to “confirm” their wish by clicking a link. It helps to filter out wrong email addresses and preserve the quality of the mailing list. It is also known as “COI” or “double opt-in.”