Issue on Flows?

  • 1 April 2024
  • 5 replies

Badge +1

Will the double opt-in email be sent to all contacts when we back populate a flow?

here’s what happened.

I created a new pop-up form and contacts go to a new list, a new welcome flow (3 emails) triggered by contacts going to the new list.

I turned on the form, and email #1 of my welcome flow. the list has double opt-in.

I tested by signing up to the new pop-up, expecting to receive the double opt-in email and welcome email #1 which is LIVE. I received the double opt-in email but after few minutes, I did not receive welcome email 1.  What happened was, I added old contacts (back populate), and the horror happened - a lot of existing profiles received a double opt-in email.

I already turned off the pop-up, and welcome email #1, but the existing contacts still received the double opt-in email.

Is that normal? Did I make a mistake in doing the back-populate?  Was that supposed to happen?

All the while I thought the existing contacts will not receive anything since my welcome flow trigger was “when someone joins the new list” I created.  Why did the existing contacts received a double opt-in email?


Best answer by Kat Mofokeng 2 April 2024, 11:16

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5 replies

Userlevel 4
Badge +11

Hey @Bobomatcha , That's a bummer to hear about the double opt-in emails going out to existing contacts. Back-populating a flow adds existing contacts who meet the trigger criteria (in this case, being on the new list) to your flow. Klaviyo treats back-populated contacts as if they were just joining the list, regardless of their previous opt-in status on that list (since it might be a new list for them).

What Went Wrong:

Since your new list has double opt-in enabled and you back-populated the list, Klaviyo automatically sent the double opt-in email to all those existing contacts, even though they might have already been opted in for other Klaviyo lists.

How to Fix It:

While you can't undo the sent double opt-in emails, you can prevent it from happening again:

  1. Segment & Back-populate: Instead of back-populating the entire new list, consider creating a segment that only includes new contacts who haven't already opted in. Then, use this segment to trigger the flow.

    This ensures the flow only targets those who need the double opt-in confirmation.

  2. Review Double Opt-in Settings: Evaluate if double opt-in is truly necessary for this specific list. If existing contacts are already subscribed to other Klaviyo lists, requiring another confirmation might not be ideal.

Always double-check your flow triggers and segment criteria before back-populating to avoid unintended consequences.

Badge +1

Thank you for your reply.
I have an additional question though.
This is a new Klaviyo Account. I imported contacts from MailChimp since we are moving to Klaviyo.

So the pop-up is new, and the list is new (I called it “Klaviyo Form Sign-Up”).  The existing contacts I am referring to were all imported from Mailchimp.  There has been no other contact who used the pop-up, except for 2 emails that I used for the test.

In this case, The (new) Welcome Flow that I back-populated is triggered when someone joins the “Klaviyo From Sign-Up” List I recently created.  There are only 2 emails in that list - which are the test emails.

So in this case…. will the other contacts (imported from Mailchimp) receive the double opt-in email after I back-populated the (new) welcome flow, even if they don’t meet the trigger?


Userlevel 1
Badge +4

Hey @Bobomatcha 

The other contacts will not receive the double opt-in email after you back-populated the new Welcome Flow. The Welcome Flow is specifically triggered when someone joins the “Klaviyo Form Sign-Up” list. Since the existing contacts were imported and not added through the pop-up, they won’t meet the trigger criteria for this flow.

You can make them go through the welcome flow though if you want to. Let us know if this is what you intend on doing and we can give you suggestion on how to do this. 

I hope we were of great help! We always here if you have more questions.

Badge +1

Hey @Kat Mofokeng 

Thanks. Just as I thought.

Only contacts within the list will receive the double opt-in and NOT the other contacts that are not in the list.


For some reason, it caused a lot of trouble last week because other contacts that are not in the list received a double opt in email and caused panic among those subscribers. I was thinking this could be a glitch? 

Userlevel 1
Badge +4

Hey @Bobomatcha 

 it’s unlikely to be a glitch in Klaviyo. By default, all Klaviyo lists are set to double opt-in. This means that when you import new contacts, they will receive a confirmation email asking them to confirm their subscription. So I believe this is why the list you imported received the double opt in email. 

You could have changed this in your list settings in Klaviyo. The default setting is Double Opt-In which is best practice. It might seem like an extra step, but it helps maintain list quality and ensures that you’re sending emails to engaged subscribers. If you have a specific use case that requires single opt-in, you can adjust your list settings accordingly.    

I hope this helped. We still here if you need us.