The Nomenclature of Opt-In

As with so many aspects of email marketing, there’s much confusion over the meaning of “opt-in.” Different camps use the same terms to mean different things. Today, an overview of the nomenclature, and who uses which terms and why.


Recipients are added to the list without their express permission. They remain there until they request to be removed.

Opt-out was long advocated by the Direct Marketing Association (DMA) as the way to go. It argued the “one bite at the cherry” principle: every business should have the right to send you one email.

Opt-out isn’t outlawed by CAN-SPAM, but most respectable marketers realize it simply isn’t acceptable. Sending email is cheap. So many organizations could theoretically send to a given individual that the number of “one bite” messages would be overwhelming.

Single Opt-In

Recipients are added to a list through a single subscription act (filling in a form on a Web site, sending an email to a specific address, or filling in a business reply card). No confirmation is sent, nor is the subscription verified.

Some call this “opt-in,” others “opt-out.” There are a number of problems with this kind of subscription. The most common are:

  • Erroneous subscription. Mistyping a single character in an email address can cause email to be undeliverable or sent to someone else. Although such errors are rare, spam is such a hot issue that even one in a million can be a problem.
  • Forged subscription. Also rare, list bombing (deluging a recipient by subscribing her to many lists) can be devastating to the victim. Whether your list can be abused in this manner depends on the sign-up mechanism and mailing frequency. Marketing lists tend to be poor tools for list bombing due to low mailing frequency (typically measured in email messages per month rather than per day). However, having to opt out of 10,000 lists is a lot of work.
  • False subscription. When coerced into entering an email address, many people will enter a false one. Many common ones are valid or use valid domains. These domains or users can end up under a virtual DOS attack (define) from false subscriptions.
  • List poisoning. Some people deliberately subscribe spam-trap addresses to unconfirmed lists. Every time a mailing is sent, the spam trap is hit, with potentially disastrous results. Identifying stealth spam-trap addresses is virtually impossible, and removing them requires reconfirmation of the list.

Notified Opt-In

Recipients are added to a list through a single subscription act. An email is sent to notify them of their addition and to enable them to opt out if they wish.

This is a single opt-in subtype, and generally suffers from the same problems. Some people call this “confirmed opt-in” because a confirmation notice is sent to the new recipient. However, most consider confirmed opt-in to require active confirmation.

The problems of single opt-in are somewhat mitigated if the notification message is sent soon after subscription. Falsely or erroneously subscribed recipients can get off the list before they’re bombarded with list email.

Confirmed Opt-In

After a recipient indicates her desire to join a list, a confirmation message is sent to the address. Affirmative action must be taken to activate the subscription.

This process is often called “double opt-in” by marketers. The logic is the recipient must perform two actions to join a list. Many in the anti-spam community call it “opt-in,” considering closed-loop confirmation an absolute requirement of opt-in. The reasoning is without confirmation (by email or other assured mechanism) the opt-in request is unsafe and unreliable.

Confirmed opt-in (COI) has two main stumbling blocks for marketers:

  • Technical limitations. Many organizations don’t have the capability to quickly and efficiently send and process confirmation requests.
  • Unconfirmed requests. By far the biggest issue for marketers is the number of unconfirmed subscription requests. Real-world numbers are hard to come by, but those I’ve seen indicate on average over 50 percent of initial requests are unconfirmed. Though this number can be reduced by good copy, subject lines, and Web sites, I haven’t seen anyone credibly claim to achieve above an 80 percent confirmation rate.

How do you decide what type of opt-in is right for which circumstances? That’s a topic for the future.

Until next time.

Want more email marketing information? ClickZ E-Mail Reference is an archive of all our email columns, organized by topic.

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