If you use another email marketing company, most likely they place a similar style of tracking. We recommend that you reach out to their support to find out if this is the case!
NOTE: In order for this rule to function properly you MUST be running the Klaviyo tracking script simultaneously. To install the Klaviyo tracking script please reference the following article:
Code to Add to Your Website
// Replace "YOUR_API_KEY" with your real API key.
Step 1: Create a Justuno Promotion, if haven't done so already you can follow this article for a basic email capture
Step 2: Head to the rules section, if you have a basic rule switch to advanced
_learnq.identify().$email != null && _learnq.identify().$email != ''
and change the rule to say "is equal to" "false" or "is not equal to" "true"
Step 4: Hit save and you are all set!