Use Klaviyo as an access control list
By default, our Klaviyo key condition signs up your customers for your Klaviyo mailing list, when they submit their email address. However, this key condition also supports using Klaviyo to establish a list of customers who are preauthorized for your content.
To use this mode, set up a Klaviyo key condition in the normal fashion: create a lock, then click "+ Add the first key", then select "subscribes to your Klaviyo list" from the list of available key conditions.
Then, after choosing your Klaviyo list, check the box labeled "Only grant access if the customer is already on this list". As noted in the form, with this mode enabled, Locksmith won't add anyone to your Klaviyo list. Instead, access will only be granted for confirmed email addresses that are already on your list.
Make sure to scroll down and change the "Mailing list signup prompt" to reflect the fact that you're checking for preauthorized access, instead of looking for signups!
Tip: To allow a customer to be on one of many Klaviyo lists, add separate keys to represent each list you'd like to check. To do this, after creating your first key and closing the configuration popup, click the "+ Add another key" button, select "subscribes to your Klaviyo list" for the new key condition, and configure it with the second Klaviyo list you'd like to check, making sure to check the "Only grant access if the customer is already on this list" box again. Repeat until you've covered all of the Klaviyo lists you need to check.