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The most common question we get in email deliverability field is arguably "why my campaigns are landing in spam folder?". This is not always easy to answer, but in general the first thing that most experts will look into is your email address gathering practices and subscription process. More often than not there are improvements to be made and some times it reveals that poor choices were made. Needless to say, most experts will try adapt your email subscription method to your business model, but there are some "generic" points to be made. Let's discuss different types of opt-in methods further:

1. Single opt-in

This particular method revolves around the most basic setups. It is convenient for most starting marketers, as it does not require any additional efforts in development in order to start growing your database size. However, most deliverability experts will look at this opt-in method as the main culprit if deliverability issues begin appearing. 

Risks: Very high.
You are risking spam traps getting into your lists, higher percentage of non-existing addresses that were mistyped, higher amount of spam complaints due to mistyped addresses being someone else's email addresses and you even may become a victim of List-Bombing attack, where your lists will be filled with gibberish email addresses by bots.

Note: long-term risks can be mitigated to a degree by implementing security mechanisms like email validation, CAPTCHA, typo corrector, etc. This is being discussed further on “1.5. Single opt-in (secured)” paragraph. 

Rewards: Very high, short term.
Your subscriptions count will be the highest using this method. In addition, it would result in no end-user friction (as no additional actions from the recipient are required) and it would not involve any additional time to develop. 


1.5. Secured Single opt-In

This method is your casual Single opt-in, secured with the above mentioned CAPTCHA, email validation or other methods, like hidden/fake fields in the form that would be filled by bots only (a.k.a. honeypot fields), email address typo corrector, etc., to protect your subscription forms from abuse.

Risks: Low.
You will already cover the majority of security issues that would lead to email addresses that do not belong to actual potential clients (or real people), being entered on your form.

Rewards: High.
You will need to invest time to secure your subscription forms, but the process for the end-user will be frictionless. 


2. Confirmed opt-In

Also known as Double opt-in. This method is the go-to method for most marketers that are trying to achieve more than a basic level of marketing law compliance. This method revolves around sending an email to the recipient with a confirmation URL, so that upon clicking the said URL the mailbox owner could verify the ownership and express an explicit consent for marketing content. 

Risks: Low.
With this method email deliverability becomes a factor, as you need to maintain a good reputation of confirmation email sending infrastructure in order to deliver opt-in confirmation email. For that, you will most likely need to implement at least one additional mechanism to protect your forms: a CAPTCHA solution on your subscription forms, an email validation tool or other methods, like hidden/honeypot fields in the form, strict IP throttling, email address typo corrector, etc., to protect your subscription forms from abuse. You will need to remove as many mistyped, incorrect, non-human-entered email addresses before the actual subscription confirmation email is sent. 

Rewards: High, long term.
Your subscription count will be lower, you will need to invest time in order to make your subscription forms full-proof and there is a certain amount of end-user friction where they will need to confirm their email address. The bright side is that in the end you will get the cleanest and mostly engaged database of recipients you can get, as they have already proven themselves that they are willing to go through multiple steps in order to receive your email. 

In addition, considering the long term, the average life-cycle of a subscriber gained with this method should be increased when compared to any single opt-in method. The reason why I am saying this is related to user psychology and cognitive bias, which is called the IKEA effect. To put it simply, when you put in effort into something, you will stick with it for a longer period of time and you will enjoy it more. 


2.5. Asynchronous Confirmed opt-in

This opt-in method revolves around providing a choice to your recipient to confirm their subscription when they feel like it. For example, your client creates a user profile and opts-in to marketing. In the beginning such email addresses should stay dormant with unverified opt-in status. An option to verify their email is provided on user profile/account (it can be done via confirmation URL or code being sent to their email address). Once that is done, the email address can be considered confirmed and opted-in for marketing. This also would allow you to resend a confirmation email whenever the mailbox owner changes their email address, thus allowing your recipient to keep their email address up to date. 

Risks: Low

Same as for regular Confirmed opt-In.

Rewards: High, long term.

The only difference with this method is that you allow your client to choose when they confirm your email. As such, your potential recipient is not being forced into a situation to react fast and it can result in even less end-user friction. In addition, this allows your recipient to update their email address at will.


I hope that after reading this you have a better grasp on which opt-tin method to choose for your business. However, do not forget that email industry is a very fluid market and it changes constantly same as your business needs may change as well. In the end, you may want to try out different subscription methods in order to find the perfect balance between best possible deliverability and your business needs. 

From my personal point of view, I would agree with what Steve Freegard (Senior Product Owner of Abusix Intelligence) said in Deliverability Summit 2022 London just this week:

"If marketers would use these two practices, they would avoid vast majority of blocklists:

  1. CAPTCHA on pages with subscription forms;

  2.  Double opt-in;"


If you wish to expand your knowledge on opt-out methods, feel free to navigate to this article:


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You can ask questions and provide suggestions for helpful email deliverability topics in the Q&A area Q&A – SAP Emarsys Email Deliverability.

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