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Single Opt-In vs. Double Opt-In: The Case for DOI


In part two of our case for finding the right subscription method for your company, let’s take a look at why the double opt-in method is a better long-term strategy.

As someone who has worked in growth for some time, I can tell you there are two modifiers that are most often associated with my job: volume and speed.

Both are a misrepresentation of growth, and usually lead to all kinds of bad habits, most at the expense of the end user. Building an email list is one of the more common areas of occurrence.

“Double it, and double it quickly.”

Typically this leads marketers to the single opt-in method of building their list. It removes friction from anyone signing up, as people simply input their email address in a form field, and they’re added to the list.

Another, albeit smaller segment of brands employ the double opt-in method of generating signups. This method could impact the size of your list, as according to Campaign Monitor, 20% of initial subscribers will not complete the final confirmation step.

Before we go on, let’s further define both terms:

  • Single opt-in (SOI) is a subscription process where a new email address is added to your mailing list without requiring the owner of that email address to confirm definitively that they knowingly and willingly opted in.
  • Double opt-in (DOI), also known as confirmed opt-in (COI), is a subscription process where a new email address is only added to your mailing address after the email address owner clicks a confirmation link in a subscription activation or opt-in confirmation request email that’s sent to them after they opt in via a form or checkbox.

Here’s why the double opt-in method is a better long term strategy…

Opening Statement

Building an email list of active subscribers is rarely a result of volume or speed. Subscriber engagement will ultimately be your determinant of success. Not the amount of subscribers, or how fast you generated them.

Presentation of Evidence and Testimony of Witnesses

Exhibit A: Increased engagement

While it’s true that added friction reduces the likelihood of a desired action, activity in and of itself should never be the sole aspiration of an email marketing strategy. Overall list engagement is a better indicator of program health rather than the size of your lists.

Easy to say if you’re a brand with a sizable database, right? Consider this: Companies that win don’t do so because of list size, but rather list engagement, and when it comes to engagement, the double opt-in method holds a clear and obvious advantage.

Says MailChimp:

“The double opt-in method ensures that you target subscribers who really want to hear from you. These types of lists have much higher engagement levels over time, which means more opens and clicks and fewer bounces and unsubscribes.”

And Campaign Monitor:

“Subscribers who ‘say yes twice’ are generally more responsive, meaning they’re more likely to open emails and click links. Positive response like this boosts your sender reputation, improving delivery rates.”

If you’re thinking, “Well, wouldn’t a single opt-in list contain everyone who would have completed a double opt-in (and then some?),” the answer is yes. However, over time this doesn’t necessarily mean more engagement. Due to the higher probability of single opt-in subscribers marking you as spam—affecting your sender reputation and deliverability—there’s a chance that less and less of your list will receive your messages over time.

For an email program to be successful, you need to maintain the long-term health of your database to ensure enough subscribers will receive your messages for engagement to matter.

Successful growth strategies hinge upon low input, high output activities in order generate results at reasonable costs. And while a larger list may not cost you more than a smaller one would, a more engaged list could generate the same—or even better—results than a bigger list containing subscribers with varying degrees of engagement.

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Exhibit B: Cleaner lists, lower bounce rates

While the added step can be a point of frustration for subscribers, it helps brands maintain cleaner lists in order to protect sender reputation and, as a result, high deliverability.

People mistakenly input incorrect email addresses. Malicious “registration bots” and spammers could commit typos during the signup process, resulting in higher bounce rates. As your list continues to grow using the single opt-in method, so do the instances of these scenarios. And because both result in incorrect or fake email addresses, the compound effect leads to lists with poor deliverability, which negatively impacts your sender reputation.

While you can certainly mitigate these risks manually, the bigger your database, the more herculean of a task this becomes. Why wait until it becomes an issue when you can address it at the beginning of a subscriber’s engagement?

Exhibit C: Reduced probability of spam complaints

Subscribers that take the extra step to confirm their subscription are also less likely to submit spam complaints. Spam complaints negatively affect your sender reputation, which in turn, negatively impacts your deliverability. Ideally you want to keep a very low spam complaint rate, lower than 0.1-0.2%. Each ISP differs and some are based on rolling averages, but a high spam complaint rate might actually get you blocked or moved to the spam folder.

So while you’re never 100% protected against spam complaints, the DOI method reduces the probability and likelihood that any spam complaints will happen and/or negatively impact your deliverability.

Exhibit D: Stronger proof of subscription

By employing the DOI, you’re also protecting against any legal recourse a person can take in response to them being “spammed.”

You have a stronger proof of subscription should you ever find yourself in this predicament. You’ll have the confirmation IP address, time, and date stamp stored by your ESP, so you’ll be able to prove that they confirmed interested in being added to your list.

Call for Witnesses

If you would like to testify on behalf of double opt-in, please submit your comments below.

Closing arguments

While the single opt-in method is the quicker way to generate subscribers, if you’re looking to significantly increase the engagement levels of your email, volume may not be your answer.

Marketers obsessing over volume only do so because it’s a perceived shortcut to higher engagement. More subscribers equals more opens and clicks, right?

Sure, if you’re talking about a list with 10x the amount of subscribers. But we’re talking about a 20% difference here, not a 10x one.

If higher engagement is what you’re after, consider the double opt-in method for building your list.

Before You Make Your Decision…

Hear both sides of this debate, what your marketing peers think, and the final verdict:

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