Single vs double opt-in for email marketing

To opt-in or double opt-in, that is the question

Should I use single or double opt-in when growing my email list? It's a question I'm frequently asked.

However I don’t see it as a binary question of one or the other and I advocate using both. Sounds odd? I’ll explain.

The common concern with double opt-in is that it requires the customer to perform the additional step of opening an email and clicking a link to confirm they want to opt-in.

Double opt-in leaks

That means there is leakage, not everyone completes the confirmation step. This could be because they don’t get the double opt-in confirmation email, don’t get around to reading and clicking the link in the email or have a change of mind.

The leakage is significant, 20% is not uncommon and I’ve heard of brands with 40% of people signing-up failing to confirm opt-in. So there is no question that single opt-in will grow a list faster.

The argument for double opt-in is that it builds a higher quality list. If the measure of quality is higher click and open rates then it’s true.

What’s better, more clicks or higher click rate?

However open and click rates are not the best measure. Consider this scenario for two lists, one grown with double opt-in and one with single. The double opt-in list is smaller because of the leakage problem.

The single opt-in list drives more clicks, even though the click rate is lower, clicks are 40 versus 37. This makes single opt-in better as more traffic has to be better.

In fact, simple logic is that double opt-in can never beat single opt-in. Since a single opt-in list will contain everyone who would have double opted-in plus more people it’s not possible for a double opt-in list to drive more traffic.

The vast majority of UK brands use single opt-in

94% of the top 100 online UK marketers agree with me, as in a study I undertook only 6% of the top 100 UK online brands used double opt-in for signup from their website.

Right now you might be thinking about the quality aspect and deliverability. If a single opt-in list had such poor quality list to the extent it materially impacted deliverability, then double opt-in could beat single opt-in.

In respect of deliverability the biggest concern with single opt-in is that accidentally or deliberately a wrong but valid email address is given. This wrong address could be a spam trap or another real person who then marks your email as spam. This can damage to your reputation.

When to consider double opt-in

Right at the start I said I advocated both single opt-in and double opt-in. The reason is that you need to consider the source and signup process in order to decide whether single or double opt-in is more appropriate. Then use single opt-in for some data sources and consider use of double opt-in for others.

It doesn’t have to be one size fits all

In short, use the right tool for the right job.

For example, if your telesales team, when talking to prospects and clients, are asking for email permission and then entering the addresses onto your list there is a higher risk of badly input addresses. You can’t be sure they ask clearly for permission and if you are incentivising your sales they might be bending the rules or worse inventing email addresses. In which case a double opt-in would be sensible for this data source – and incentivise the sales team for valid double opted-in addresses!

Perhaps you have a quote process or barrier page to get a download. Here the primary motivation is not to sign-up to your list but to get past your barrier. Again this means a higher risk of a random but valid email address.

Contrast with a signup form on your website, here the only motivation to complete the process is if someone does indeed want to sign up. There should be no problem with single opt-in.

If quality remains a concern, there are also email address verification services such as StrikeIron and BriteVerify that can verify an email address in real time and so improve quality at point of data capture. With one of my clients email addresses are input by a sales team into the CRM and we use StrikeIron to improve quality.

If you still are worried about list quality when using single opt-in, there is a totally different approach. Use single opt-in, let people into your list easily. You’ll hopefully impress and engage them with great offers and content. If after a number of emails since signup they still haven’t engaged at all and you’ve tried your best, then remove them. Whilst a dry request to confirm opt-in may not be very engaging hopefully dangling real content in front of someone will be.

In some countries, such as Germany, double opt-in is very often used. It’s not strictly a legal requirement; however the level of confirmation required makes double opt-in the only practical way of meeting the letter of the law.

Finally my good friend and email guru Mark Brownlow from Email Marketing Reports gave me this good advice about reducing leakage if you must use double opt-in

“Don’t rely on standard system default confirmation mails to keep leakage down. Apply the same rigour to the design and copy you give your marketing mails. Test out different subject lines and on the sign-up confirmation pages let customers know that another step is needed”