Hey, @snoozygummy .
Thank you for joining this thread!
Based on my knowledge, third-party mailing services (eg. Klaviyo, Mailchimp, etc.) does recommend using the doubt opt-in feature from Shopify so you may still see the “Pending” status for some of your customers. Some of these mailing service providers may also make it a requirement for you to enable the double opt-in feature based on the store’s location, as some regions have privacy laws enforcing how customers can be subscribed to a newsletter.
That being said, since Klaviyo is a third-party app, then the app developer is always available to assist you. Simply reach out to Klaviyo through the contact information found in the Support section of their app’s page or you can contact them directly from within their app.
I noticed that you’re a new member of our Shopify Community! Once you’ve resolved this issue with Klaviyo, I’d love to hear more about your experience so far and share some resources to help you get started.