by Kirill Popov

Double opt-in subscription policy refers to a closed loop confirmation method of subscribing new members to your mailing list. Double opt-in adds another step a potential subscriber has to take in order to become a member of your mailing list.

When the subscriber enters an email address into a sign-up webform, that address is temporarily held and a follow up message is immediately triggered to that address. The message includes instructions for the subscriber to take some sort of action (reply, click a link, etc…) to confirm the address as valid and that the subscription request was intentional. Only then, after the confirmation is received, the held address is added to the active mailing list. Ideally the confirmation step is logged and the timestamp, IP address and/or unique user id is kept on record.

Double opt-in is a useful addition to the subscription process for a couple of reasons:

Prevents erroneous subscriptions. Often, simple misspellings of common user names or domain names may cause email messages to begin sending to a completely unintended address. Not only do you lose an interested subscriber, but you gain a user that will most likely cry foul and complain of spam.

Prevents malicious subscriptions. A popular nuisance tactic in the internet age is to subscribe someone who really ticked you off to as many mailing lists as possible, sending them a mountain of email. This creates a terrible headache for the victim and turns your newsletters into tools of harassment.

Provides an audit trail. Having double opt-in confirmation logs allows you to refute any spam complaints that may come up. Double opt-in is seen by mail administrators as the most privacy conscious way of handling the subscriptions; in case of any corporate filtering, they will be more apt to whitelist your newsletters if confirmation logs are available. And last, but certainly not least, confirmation logs protect against anti-spam legislation by providing evidence of solicitation.