What is double opt-in in email marketing?

What is double opt-in in email marketing?

The usefulness of opt-in, and specifically double opt-in, goes beyond what we might think at first, so we'll look at it in detail in this post.

Far from being a problem, this process is actually a very useful tool for your email campaigns.


We're going to focus mainly on the advantages of double opt-in, leaving aside the apparent convenience offered by single opt-in, in order to obtain the maximum benefits offered by this tool.

Opt-in in email marketing explained using non-technical words                      

In an idealized view of the opt-in process, things would work more or less like this:

1. You have your website and you include a sign-up form on it asking for the visitor's email address.

2. Then, when visitors access your site, if they are interested, they type their details into the form, including their email address, and submit the form.

3. In this way, the visitor will be registered on your contact list.

4. and from then on, you can talk to this person through newsletters and mass mailing campaigns.

Esse processo que vimos seria o processo de opt-in simples e isso nos leva à pergunta mais lógica: se é tão simples, por que seria necessário usar outros métodos de opt-in? Por exemplo, double opt-in.

There are several answers to this question. Read more.

Mistakes and problems in the opt-in process

People make mistakes. Forms can warn us if we misspell something (for example, if we don't put in the domain extension), but if the mistake we make is very small, such as swapping a domain name for a username, that could be a problem.


However, if the mistake we make is very small, such as swapping one letter for another, the form won't warn us.

Because in a simple opt-in process, if there are no serious errors, everything seems to have worked fine.

What happens if the error isn't detected?

Nothing serious or something very serious. Well, the wrong email is registered in your contact list and, when you send the mass mailing campaign, these emails will bounce, they will generate an error if they don't exist, at best. And at worst, the email will be sent to someone else.

This could go further and have legal implications, as you would be sending your emails to people who have not given their consent.

Now you might think that the chance of these things happening is low and that the risk is offset in exchange for offering a simple and quick opt-in process.

The reality is that it will depend on:

  • Luck
  • The number of emails

If you send  a lot of emails, you could start facing some serious problems. But things can really start to get ugly when it's no longer a matter of human error.

Bots and malicious registrations

There are many scripts that can affect your email marketing campaign. Although this is not the first possibility that comes to mind, it is the most serious issue in terms of the damage it can cause us.


What can happen in this case is that a bot or script is used to generate false records in subscription forms.

Why does this happen?

The issue of bots is complex. A bot is a small computer software, and the ones we are dealing with here are designed to crawl web pages in search of forms.

Any kind of form, whatsoever.

Most likely, these bots are looking for contact forms or blog comment forms:

  • To leave fake comments with links to their website (presumably for SEO purposes).
  • To try to apply phishing techniques (information theft).

What happens is that the bots can't tell one form from another (or don't care) and so they fill in all the forms they find. With fake data, of course.

As a result, you could end up  with hundreds of fake emails on your contact list, which can be a problem for your campaign as there would be lots of errors and bounced emails.

Little by little (or quickly, depending on the number), this will damage your email marketing strategy.

Malicious opt-ins

On the other hand, it is also possible to be attacked by malicious people who are trying to register thousands of fake emails on your forms.

What could be the motives behind this? Many, from people who want to harm your company for whatever reason, simple coincidences or hackers who are learning and testing.

It's very difficult to know, but it's something that can happen.

Considering the problems, what solutions are available?

There are various solutions to these problems, and one of the most commonly used is the use of a captcha.

What is a captcha?


Surely, on many web pages you've seen forms that ask some kind of question to allow you to register, or show you some images from which you have to choose a specific pattern.

Captcha is a secure and effective system, although it has the disadvantage that the user has to answer the captcha, which can be a bit annoying. (especially in some cases where the captcha can be particularly complicated).

In addition to the possible discomfort for the user, although it is a solution to the problem presented by bots, the reality is that the user may have problems or be unable to respond to the captcha:

  • Mistakes the user can make when typing the email.
  • And malicious users who register other people's emails.

Therefore, captcha is a system more geared towards protecting forms against bots and other automated software.

However, it doesn't prevent human mistake and other malicious uses, such as the situation we mentioned at the beginning, where, due to a registration error, the email reaches someone else.

This is inevitable when using this type of tool, so the most effective solution is double opt-in.

How does double opt-in work?

Double opt-in is a process that works as follows:

1. You have your website and you include a double opt-in subscription form on it which asks for the visitor's email address.

2. Then, when visitors access your site, if they are interested, they fill in the form with their email address, sending the information to the server that manages the subscriptions.

3. In this way, the person is registered in your contact list, but inactive.

4. As soon as the user leaves their email address in the form, they will receive a confirmation email.

5. When the visitor clicks on the link in the confirmation email, their contact, which was already saved but inactive, will be activated.

6. And from then on, the new subscriber will be able to receive your mass mailing campaigns and newsletters.

The process is just as simple as opting in, except that the visitor has to click once more.

This process guarantees that:

  •  The email is correct, otherwise they wouldn't receive it.
  •  The subscription was made voluntarily.

It is therefore the safest option for avoiding problems. And, to a certain extent, it also protects against bots, as it is not common for bots to confirm an opt-in. If this is happening, you can combine the double opt-in process with a captcha, for example.

Why do some companies prefer not to use double opt-in?

There are several reasons why some companies may not want to use the double opt-in process in their email marketing strategy:

Lower conversion rate

The double opt-in process requires users to confirm their subscription before being added to the mailing list.

It is normal that some users won't confirming their subscription, which can reduce the conversion rate and the size of the mailing list.

It is a more complex method

The double opt-in process adds an additional layer of complexity to the subscription process, which can be confusing or off-putting for some users.

Fewer emails sent

By using the double opt-in process, fewer email addresses will be added to the mailing list, which can reduce the number of emails sent and limit the reach of the email marketing campaign.

However, it is important to bear in mind that the double opt-in process can also offer significant advantages, such as a cleaner and better quality mailing list, a more targeted email marketing campaign, higher open and click-through rates and a more positive sender reputation.

So while there may be some disadvantages to using the process, many email marketing experts recommend it as an effective practice in managing email marketing lists.

Are there ways to avoid the negative effects of double opt-in?

Yes, there are ways to limit the negative aspects of the double opt-in process in email marketing and maximize its benefits. Here are a few suggestions:

Simplify the confirmation process

To reduce the complexity of the double opt-in process, it is important to ensure that the confirmation email is clear and easy to understand.

Use simple, concise language and provide clear instructions on how to confirm the subscription. In addition, you can simplify the confirmation process by using a confirmation button instead of a link.

Offer incentives to convince users to confirm the subscription

You can offer subscribers incentives to confirm their subscription, such as discounts, gifts or exclusive access to content.

This can help increase conversion rates and encourage subscribers to confirm their subscription.

Clearly explain the advantages of the double opt-in process

To encourage users to confirm their subscription, it's important to list the advantages of the double opt-in process, demonstrating what they will receive when they confirm their subscription to your mailing list.

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