What is “confirmed opt-in” (COI)?

Confirmed opt in (COI) is another term for double opt in, emphasizing the confirmation step. After initial signup, the subscriber receives a verification email and must click a link to confirm their subscription.

COI provides documentation that the subscriber actively confirmed their address. This creates stronger evidence of consent than single opt in, which cannot prove the form submitter owned the email address.

M3AAWG and most best practice frameworks recommend COI as the gold standard for list collection. While it reduces initial subscription rates, the quality improvement in terms of engagement, complaints, and deliverability typically outweighs quantity reduction.