API to subscribe new users to email isn't working with double opt-in

  • 1 August 2023
  • 5 replies




I have integrated via the REST API and I am trying to add my own email to a list.


When I do so without double-opt-in enabled the email gets added to list list and the profile is created.


I then try to turn on double opt-in, and now the email does not get added to the list.  Further there is NO EMAIL sent to this address. I tried to remove the email and try a new one but no luck. Please help as my 60 days support is over.


If I can’t get this resolved in the next 12 hours I will definitely churn.


Best answer by retention 1 August 2023, 21:55

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5 replies

Userlevel 7
Badge +57

Hi @amk22012, welcome to the community!

So, when the double-opt in is enabled for a List, and you are using the “Create Client Subscription” API call, then the email is only added once the user confirms the double opt-in request.  This is behaving by design for double opt-ins.  You can read about the double opt-in process here:

As you already mentioned, you can decide to use Single Opt-In if that fits your business requirements. 

However, if you just want to create a Profile in Klaviyo, but not Subscribe them to a List, you can also add a Profile to Klaviyo using the “Create or Update Client Profile.” This makes no opinion on their marketing consent status and simply creates a Profile in Klaviyo.

Hope this helps!  



Yes, I already know this. I am saying that my double-opt-in email is not being delivered. Possibly my IP is blocked??

Userlevel 7
Badge +60

Hey @amk22012,

Have you also checked your inbox’s other folders such as a promotion, spam, or junk? Sometimes the double opt-in email will land in those folders. 

In the same train of thought, do you have any inbox or networking filters through your DNS or did you happen to previously have a dedicated/authenticated domain? These are some common causes for the double opt-in email to be either blocked or placed in spam when self-testing. 

How often are you testing? If you’ve been testing this a number of times in a short period of time, you may have hit the list bombing prevention system


Hi @David To,

I am using API ( to subcribe a double opt-in list. Sometimes email is being delivered, but sometimes email is not being delivered. How I can check it work or not? How I can add IPs of my app to whitelist of Klaviyo?


Phuong Vo

Badge +2

Hi, same problem here. When list is single-opt-in then “profile-subscription-bulk-create-job” endpoint adds profile to list with consent status = subscribed.

If I change lists opt-in process to "double-opt-in" and subscribe new email it does not receive “Email Confirmation” nor is added to list. Only profile with status "never subscribed" is created.

Maybe the problem is the account is "test account?"


EDIT:  It works - BUT I found confirmation email in SPAM folder

gmail says: 

Why is this message in spam? 

Lots of messages from were identified as spam in the past.

How can I avoid that?


EDIT2: I already found how to setup dedicated domain:


Thank you everything works just fine :)