Why are my newsletter subscribers not being added to my list?
If double opt-in is enabled on your account, users won't be added to your Newsletter list until they confirm the opt-in email that Klaviyo sends to their inbox. By default, all lists in Klaviyo have double opt-in. What this means is, after someone signs up, they have to go into their email inbox and confirm their subscription. After completing this step, they are added to the list. If you'd like to remove double opt-in any list, you'll need to upgrade to a paid account and email us, as the option to disable is available there.