Sep 23, 2011

Double Opt-in vs. Single Opt-in Stats

There’s a long history of conflict between double opt-in and single opt-in list confirmation. Ultimately, email senders have to choose between list size and list quality. As an ESP, we tend to care a lot about the quality of your lists. After all, our IP reputation is at stake.

A handful of bad lists can ruin the party for our million good users. That’s why you’ll hear us talk so much about double opt-in list confirmation. If you don’t know what I’m talking about, check out Ben’s blog post from 2005. It’s kind of required reading if you want to understand the stats below.

When talking about double opt-in, we tend to hear customers say, "Why should I make it harder for people to subscribe to my list?" I get it. After all, double opt-in does require people who want to get emails from you to… open an email from you. It’s an extra step, but I think it’s one you can afford. Cutting corners in list collection tends to generate bounces, blacklisting, spam trap hits, and other nasty stuff that can tank your emails.

The question is, will using double opt-in really improve the stats that matter: opens, clicks, bounces, and unsubscribes?

We took a random sample in our database of 30,000 users who’ve sent at least 10 campaigns. We wanted to make sure they’d have enough stats to make the analysis interesting. These users had list sizes from 500 to 1.5 million. Some of them send every day, and some of them send a couple of times a month.

Higher Stats

After pulling this broad sample, it was fairly easy to aggregate their campaign stats and let the numbers do the talking. I think you’ll like what they have to say. As you can see, double opt-in lists have better open rates.

Unique Opens: Double Opt-in vs. Single Opt-in
Unique opens means we don’t count multiple opens per subscriber.

It’s important to keep in mind that these are unique opens. That means we only count the first open per subscriber. It turns out that while double opt-in has a 72.2% increase in unique opens, they have a 75.6% increase in total opens. So not only do double opt-in lists get more opens, they also get more multiple opens per subscriber. Cool, right?

Okay, so people are opening your emails. They’re also clicking your emails. The chart below shows that double opt-in lists have a 114% increase in clicks as compared to single opt-in lists. That’s right, it’s more than double.

Recipient Clicks: Double Opt-in vs. Single Opt-in

Lower Stats

There are a few stats you desperately want to lower. The first would be bounce rates. Bounce rates can get you kicked out of MailChimp, which would be terrible. We’re much more strict on hard bounces than soft bounces, and using a double opt-in list can lower your bounce rate by 48.3%. The soft bounces are 25% lower, which isn’t bad either.

Hard Bounces: Double Opt-in vx. Single Opt-in
Soft Bounces: Double Opt-in vs. Single Opt-in

Finally, you’ll be pretty interested in the unsubscribe rate. The higher your unsubscribe rate, the more aggressive you have to be about list growth. For the desperate email marketer, that can mean making risky choices with your list. Double opt-in lists have a 7% lower unsubscribe rate as compared to single opt-in lists. I wouldn’t call that a miracle number, but it does give you some breathing room. It also proves that a lot of those single opt-in subscribers don’t want your email. Keep in mind, unsubscribing is the nice way a disinterested subscriber responds. They’re just as likely to hit the spam button and forget about you. If at all possible, let’s avoid that!

Unsubscribe Rate: Double Opt-in vs. Single Opt-in

By the way, we’re not the only ones who care about your list quality. Major ISP’s are watching what you send, how many opens you get, how many clicks you get, and definitely how many spam complaints you get. They can choose to throttle your campaign or simply send it to the spam folder. It definitely pays to be vigilant. As Freddie Bueller once said, "Email moves pretty fast. If you don’t stop and look around once in a while, your subscribers could miss it."