Single opt-in, Double opt-in, or The Best of Both Worlds?

Single, double, or soft double opt-in?

Wondering whether you made the right choice regarding opt-in across your mailing lists?

No easy decision to make, we know.

single opt-in vs double opt-in

The idea is that choosing opt-in process is a function of your business goals and marketing strategy.

What it really boils down to is whether you are taking the long-term approach or a “move fast and break things” approach.

Are you trying to build an email marketing list quickly?

Even if this means you are sacrificing some of your security standards?

Or it potentially violating a data protection law?

It’s all a matter of perspective.

What are you looking for?

1. What is opt-in, to begin with?

2. What is single opt-in (SOI)?

3. What is double opt-in (DOI)?

4. Hybrid / soft double opt-in (SDOI) definition

5. Single Opt-In Pros

6. Single Opt-In Cons

7. Double Opt-In Pros

8. Double Opt-In Cons

9. Opt-in stats

10. Take our SOI/DOI quiz!

11. Key Points to Consider Before Choosing Single or Double Opt-in

12. Here’s an Infographic for You!

13. GDPR Considerations

14. TL;DR

What is opt-in, to begin with?

what is opt-in

Opt-in is the subscription method every email marketer uses on their mailing lists.

More specifically, opt-in refers to how a business enables their users to become subscribers.

There are three types of  opt-in: single, double, and soft-double opt-in, all of which are explained below.

Note that it is not necessary for a business to have a single type of opt-in across its mailing lists.

Every mailing list can come with the most suitable opt-in method with respect to its objectives: list growth, deliverability rates, and so on.

What is single opt-in?

Single opt-in is a subscription path that allows users to become subscribers immediately.

As soon as they enter their email address and fill in all required fields, they start receiving the communication of the brand.

This process does not require the owner of the email address to confirm that it was in fact them who actually requested to register for the newsletter.

Single opt-in does not require users to explicitly and consciously take any other action after entering their email.

What is double opt-in?

Double opt-in, also hard double opt-in, is the confirmed process for users to opt-in to receive communication from a company.

That is, everything from newsletters, to blog posts, updates and promotions must be primarily selected for the communication to be completed lawfully.

For example, when a user checks a box and enters their email address to a signup box, they receive an email asking them it was them who actually requested the signup.

Then, the user will confirm by clicking the verification link. Only then will the user join the newsletter community of the brand.

In case the user does not confirm the link, they cannot be contacted by the company under any circumstances.

What is hybrid opt-in? Or, in Moosend speak, “soft double opt-in”.

soft double opt-in

Soft double opt-in is Moosend’s handy way to reach end-users who have

a) opted in
b) but the digital marketer lacks the proof of their consent.

For example:

Let’s say a user has provided their contact details at a conference (or offline). For them to receive an email, the business needs to provide consent.

And when it comes to consent, a handwritten email address won’t cut it.

The email address could be incorrect, or even fake. And that’s going to mean either bounced, or unwanted emails.

That’s where soft double opt-in comes in.

It allows a digital marketer to send their marketing campaign without having prior confirmed consent.

Here’s how it works:

  1. Before the email hits the recipient’s inbox, the user gets an automated (customized) email from the brand.
  2. This email requests the user to click the verification link in that email.
  3. As soon as the user clicks the verification link, Moosend automatically updates the recipient’s status to “Verified”.
  4. If the user doesn’t click, then the status remains “Unverified”.
  5. If they still don’t click, then the email marketer can manually send another email, following explicit user request.

In summary:

It is essential that user request be in a format that can be used as proof, e.g. an email.

But with double-opt in, there’s no way to reach out again to users who have not confirmed their consent.

It would have to be through email that the user would request emails (which would be held as proof) for the Admin to verify them manually as “Verified by Admin”.

So soft double opt-ins make it easier to gradually verify your list as you go. 

Single Opt-in Pros

single opt-in pros

Get “speed-of-light fast” list growth

If you are on the fast track to email marketing list growth, this is your best bet.

Quick and easy, single opt-in guarantees a smooth experience for the user.

Every user simply enters their email address to the signup box and they instantly join the team.

This way, digital managers skip the confirmation stage and don’t risk losing their leads.

Why so?

Losing leads is associated with a confirmation email (which is used in double opt-in) and is normally sent as soon as a user registers.

What can go wrong is that this confirmation email can hit the spam folder, for example.

(Maybe you are now convinced that you need to set everything up properly to leverage your deliverability score, just maybe.)

This way, your new users jump start their freemium plan.

Keep high engagement intact

Who would say no to engaged super-fans from the get-go?

The more call-t0-actions you include in your first email, the faster your users are to start disengaging with your brand.

Single opt-in involves no confirmation emails, therefore there are no actions mediating subscription!

This is ready-to-wear level of fun, rather than waiting list kind of situation. (But hold that thought.)

Single Opt-in Cons

single Opt-in Cons

No good thing comes without a drawback, so best be prepared about what you are signing up for when choosing SOI (pun intended).

Low lead quality & Harassment

Single opt-in raises the risk of having a mailing list of low-quality leads. For example, third parties could be adding users to specific mailing lists and newsletters to use it against them. Yes. Welcome to the 21st century.

In that respect, SOI leaves your subscribers unprotected and exposed to such malicious practices.

For one thing, digital managers could be getting more spam complaints due to delibarately wrong email addresses.

You see, malicious competitors could try to hurt your database with such emails. In return, they would get a stronger database, and you’d be suffering a low deliverability. Why?

Lower deliverability rates

SOI takes its toll on deliverability figures; compared to DOI lists, a considerable number of SOI-type mails don’t make it to the inbox.

Lower engagement levels

Also, engagement runs low in these lists. The mere rate at which users subscribe to lists cannot reflect an all-time-high record of engagement, naturally.

Fix This: You can fix your lower engagement levels through Moosend’s Website Re-engagement automation, which is readily available (at no extra cost).


Mailing lists with SOI also require more maintenance time; spam and hard bounces must be cleared out of the database regularly.

Fix This: You don’t have to worry about maintenance on the Moosend platform. This is an automated procedure so that we keep all lists in tip-top shape!

Sender Reputation Might Be Affected

You could be damaging your sender reputation as we speak. SOI could result – at one point or another- in a large number of “bad” addresses.

This means that there could be a higher bounce rate or spam reports.

Typos Might Cost You Subscribers

Not everyone has activated AutoFill forms. Ergo, mitsaeks hapepn.

For example, a user who subscribed but doesn’t get the Welcome email will check back. (Read here more reasons why Welcome emails matter).

Otherwise, a user who hasn’t heard from you in a while will check back to see what happened with the email.

Fix This: A counter-measure to face this would be to runs ads across social media or other platforms that resonate with your brand, audience-wise. This will help you stay a top-of-mind brand, and get people to remember to check their inbox.


Another way to fix that would be to ask users to confirm their email address by typing it a second time. Should there be no match between the two, the user will know to make corrections.

Putting content up for grabs is not list-growth friendly necessarily

Suppose you publish premium content that is gated.

Those who want to download it directly from your site could just enter a random or fake email address.

You can’t do that in DOI lists. There, users see a message reading “You will receive an email shortly and will need to verify your account”, so those with cheating intent know in advance they can’t get naughty.

So, if you really want your premium content to get you some place, even if shared for free, then maybe SOI is not your cup of tea.

Open rates are not Everest-high

Besides deliverability matters, did you know that open rates are also affected by SOI in the long term?

They could be skewed by deliberately or unintentionally wrong email addresses.

This is why you should keep an eye on these numbers, so that you can be alerted timely.

Industry concerns might impact your opt-in method of choice

If you are in healthcare or work in financial information, email marketing would require stronger, explicit permission on the user part to register than SOI.

Same goes for marketing to minors.

Double Opt-in Pros

double Opt-in Pros


You won’t be seeing much of those stomach-dropping bounce rates.

Your DOI lists are crazy engaged and super verified, because everyone was interested enough in your newsletters to confirm their subscription.

This is rather self-explanatory, but many of SOI’s cons are DOI’s pros.

Therefore, with DOI you get lower bounce rates, zero risk of bad email addresses, no unsolicited emails to unaware individuals.

High-quality leads

If you choose quality over quantity of leads, then DOI and high quality leads go hand in hand!

The reason being, that those who have interacted twice with your business to confirm their subscription to your newsletter are just about the right level of engaged.

No spam folder surprises

A side-benefit of this is that users are expecting your email -provided you have notified them explicitly beforehand- and know to look for it in the Spam folder.

This way, you are marked as a contact and your email marketing magic can get to work.

Spam free

There is no place for spam addresses in your lists. With DOI, everyone must confirm their business.

If a bot is behind the opt-in, it will not manage to confirm the email address anyway.

So, your list is as healthy as a horse! (Sounds even weirder when referring to a mailing list, right.)

No extra charges for confirmation emails on Moosend

Oh, the best part? Even though DOI involves two emails, you are not charged extra: on Moosend, our plans are subscriber-based, not email-base. Hoorray!!

Bonus Pro

Here’s a DOI best practice bonus tip: set up DOI for your mailing list and an automation to go with it.

This way, as soon as your new subscribers have confirmed their accounts, they activate the onboarding drip campaign!

Finally, if you are offering a freemium service, DOI is a great choice, particularly because your users are so engaged to get free access.

A confirmation link in the mailbox will have them jumping up and down with excitement!

Double Opt-in Cons

double Opt-in Cons

I wish I could tell you that choosing an opt-in method was easy and straightforward, but it’s not.

List growth takes more time

Double opt-in is all fun and games, until you want to grow your list considerably.

Building a marketing database on the basis of DOI will take longer.

But this is not something that an automation cannot cure!

Fix This: On Moosend, we offer a growing list of automation templates, complete with new triggers and actions for your subscribers. So, you can choose from Website Re-engagement, Onboarding, and many more.

Of course, at all times, you must make sure that your automations do not clutter the subscriber’s inbox or overwhelm them.

Avoid that at all costs by regularly reviewing user experience.

Subscribe to the newsletter yourself and check your overall inbox experience.

See if your company’s email jumps out the inbox noise.

Does your company’s email stand out?

Teenage audiences may not check their audiences often enough

Younger audiences might not check their mailboxes as regularly.

The challenge? They might get caught up in something else and forget about the confirmation email from you.

Or they could ignore it altogether. (Ouch!)

Fix This: One way around this possibility could be to spruce up excitement about the confirmation email.

For example, you could notify them upon entering their data that they’re in for a 20% discount as soon as they verify their link.

So, you get a confirmed email address and a first purchase! User engagement at its best!

Attention span is dropping over the years

Whether it’s an individual characteristic or simply a sign of our fast-paced times, short attention span is real.

There are quite a few variables that might affect that.

For example, the time when your subscribers read your email could be rush hour for them.

(Worse, it could be lunch break and they might get carried away over the latest avocado-level fad.)

Fix This: It’s all about foreseeing user behavior and designing accordingly.

Act proactively:

1. As soon as the user enters their email they should be redirected to a landing page.

This should be optimized for reminding users to check their email.

Remind them why they need to confirm.

Craft a reminder message that underlines the confirmation email requirement.

Spice it up with an additional incentive, e.g. a freebie or a discount that expires in a week from that moment.

Make it all about them.

2. Make sure the confirmation email is triggered within seconds, not minutes. Be fast.

3. Keep the confirmation email as short as possible. This is no time to showcase your creativity, just go for functionality.

Get them to click and head over to your website to shop.

What if they still don’t click? Foresee that.

A. Set up an automation through your Moosend account to send a Webhook to Zapier or your custom software. 

Essentially, your unconfirmed users will get a reminder message on, say, Intercom when they visit your website.

This will ask them to head over to their inbox (or Spam folder) to confirm. Aaaand get a discount, maybe.  You should see the engagement in that!

B. Make it possible for your subscribers-to-be to re-receive the confirmation link to their inbox, in case they deleted it by accident.

Through your CRM software (e.g. Intercom, etc.) target your unverified users on-site to notify them they haven’t confirmed their subscription.

Email Marketing Opt-in Stats

email marketing opt-in stats

Hard facts for our stats:

Fact 1: For every dollar you spend in Email Marketing, you get approximately another $40 in return.

1 dollar investment=40 dollar return.

Impressive, right?

This makes it all the more important, then, to ensure high performance of emails.

But, first things first.

How do we ensure high performance?

Fact 2: Deliverability is a requisite in this one.

Set up your SPF and DKIM.

Set up an Abuse Reporting Mailbox.

 Read the Ultimate Guide we wrote for you.

Fact 3: Spam and bounce are a major hindrance to performance, as well.

Many users perform a spam- and bounce-free maintenance every once in a while.

On Moosend, this procedure is not manual; accounts rid their spam and hard bounce addresses.

This improves the sender reputation and overall performance of your email marketing.

Hard fact based on actual stats: To conceive the sheer scale of spam abuse and implications, consider this: 

Back to the original thought, to get $40, all things equal, one must spend $1.

You are adding value to every single dollar you spend, when you maintain a golden deliverability standard and spam-free, bounce-free records.

Once we have that figured out, let’s proceed to opt-in stats.

Double opt-in stats: Internationally speaking, litmus found that in 2014 double opt-in claimed a staggering 45% of the opt-in pie in some countries, such as Germany.

This was three times as high as the respective figures in countries such as Italy or France, and almost 10 times higher than UK’s.

How have things changed over the past few years, especially under GDPR?


As a result, the double opt-in price to pay for quality is 20% of your list. Or, to put it differently,

So single opt-in is better, no?

Well, not so fast.

In SOI lists, typos, misspells, or fake addresses account for 10%.

And you might want to estimate an additional 1-2% for hard bounces in SOI.

Let’s consider this example:

You run an eshop and your list is 10.000 emails long.

With Double Opt-in, you lose about 2.000 of them to confirmation links.

That leaves you with 8.000 emails.

These 8.000 DOI subscribers show a 3-4% CTR.

In other words, 320 subscribers will make a purchase on the website.

So, with email marketing and automations, you can get a 40-fold return on the initial amount you spent.

With Single Opt-in, you get instantly a 10.000-email long list.

You lose about 1000 of those to typos or fake addresses, so that’s 9.000.

A small 2% list decay is due to hard bounces in your list equals 180 subscribers you wave goodbye to, ergo 8,820 remain on your list.

Finally, getting half the conversion rate of DOI lists, an approximate 1,5-2%… right: 176 users convert.

What kind of list are you in for?

What should you keep in mind?

You have access to soft double opt-in on Moosend’s platform. Why not give it a whirl?

Take this quiz to inform your decision over SOI/DOI:

You have an email database.

You have created multiple mailing lists.

Your relationship and type of communication with each one of those mailing lists is different.

You are looking for a different opt-in method for each one of them.

There is really no “one-size-fits-all” opt-in method.

To get started, pick a list.

As soon as you’ve finished the quiz, take a look at your score.

Is your score more on the SOI side or the DOI side?

powered by Typeform

Key Points to Consider Before Choosing Single or Double Opt-in

1. If you are trying to build a list quickly, then single opt-in is probably a better choice.

We recommend putting an automation sequence in place. For example, a Re-engagement automation creates a monitoring loop over the engagement rate of your subscribers.

For instance, you can set a minimum for, say, the number of emails your subscribers open per month or over a time period.

Those who don’t satisfy that minimum will trigger a Re-engagement campaign.

If that does not perform either, maybe you should consider saying goodbye.

These unopened emails and disengaged subscribers are hurting your open rates and sender reputation.

2. If you are acquisition-oriented rather than retention-oriented, SOI is for you.

With SOI lists you can be sure that subscription processes are smooth.

But smooth seas never make a skilled sailor, so factor lead quality in, too, before you choose SOI.

3. Who’s afraid of hard bounces and spam complaints?

Answer A: “No, not me, nuh-ah” – Then, go ahead and choose SOI. Just keep in mind you’ll need to spend some time cleaning your database.

Answer B: “I don’t do database cleaning” – DOI is your new best friend.

4. Are you looking for subscribers who are primarily interested in your newsletter?

If the main source of newsletter subscriptions is a pop-up, SOI looks like the right one for you.

But it also might be the right one for spam bots, as well.

On the other hand, if your mailing lists are your customers who register for your product/service, ensure that the signup box is not pre-ticked.

Are subscribers signing up for competition purposes, freemium plans, or free content upgrades?

All of the above give you leverage. The high level of engagement on the users’ part is enough motivation for them to click the confirmation link!

5. You have to choose between Quality and Quantity. What’s it going to be?

If you said Quality, say hello to DOI, hands down.

If you said Quantity, SOI is waiting for you!

Do you want a little bit of both? Head over to your Moosend account and choose soft double opt-in.

Are you trying to visualize all this information? We did it for you!

To illustrate our points (pun intended), we made this infographic for you.

Because, who doesn’t enjoy a seriously fun read, anyway?

Get the highlights of the ultimate article on opt-in method pros and cons, in a visual-friendly format.

You are the cool rockstar marketer who shares these awesome opt-in stats with colleagues and the community.

It will be highly appreciated – trust us!


Single Opt-in versus Double Opt-in infographic

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GDPR Considerations

gdpr opt-in Considerations

The upcoming General Data Protection Regulation (GDPR)  has sparked up quite a conversation in digital marketing circles.

Virtually on a daily basis, our Support Team receives dozens and dozens of our customers asking us where GDPR requires double opt-in.

It would be wrong to say it specifically states so.

In fact, GDPR is a law. And, naturally, there is the spirit VS the letter of the law situation.

Does GDPR go hand in hand with double opt-in? Or maybe single opt-in could be single opt-in friendly in certain cases?

None of the 99 articles of GDPR states that users should switch to a specific type of opt-in.

GDPR is destined to protect the personal data of every European citizen.

This has different implications for every industry collecting, monitoring, processing or handling personal data.

To that respect, email marketing practices must be safeguarded by certain principles.

One such principle is the data protection and transparency of processes.

In Email Marketing, one very common challenge is ill-intentioned subscribers or malicious competitors, or spam bots.

They will register fake or bad addresses, or they might enter other individuals’ personal emails.

In the first case, you might hurt your sender reputation in the long term.

In the second case, an individual might have their reputation, professional or personal, ruined.

Of course, no bad deed goes unpunished, but why let it get there if you notice red flags along the way?

Again, we do not suggest that DOI is better than SOI.

We are pointing out the weak links in the opt-in methods so that you can prepare accordingly.


  • Single Opt-in
SOI Pro: You grow fast. Your users enjoy a fast jump-start of their subscription.


SOI Con: You weed out your database for spam and hard bounces.


  • Double opt-in


DOI Pro: You invest in high-quality leads that perform. These leads stay with you virtually forever. They increase your opens, CTR, and conversion.


DOI Con: Some subscribers might go amiss if the confirmation email hits the Spam folder or they forget about it altogether. It takes longer to go big.


  • Soft double opt-in


SDOI Pro: Flexible tool for digital marketers as it gradually confirms your subscribers for you.


SDOI Con: It may or may not take longer to verify all subscribers in the list.


1. What is GDPR?

2. GDPR Email Marketing Checklist: Where Do You Rank?

3. 14 Things You Wanted to Know About GDPR and Were Too Afraid To Ask

4. Raise your GDPR Compliance Score with Douple Opt-in

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