No worries, we are here to demystify it for you!
The Lead email address you collect from your leads before they get to see their results in your quiz content serves as the unique identifier for that lead on LeadQuizzes, as well as in any CRM/EMS you are using.
Meaning that when you want to pass your lead information from your LeadQuizzes content to whichever CRM/EMS, the Lead email address is required to be able to record and identify this lead.
However, with the LeadQuizzes updated Form Fields feature, which allows you to add a skip option to your LeadQuizzes Form Fields, your quiz takers can now use this option to skip giving their details (lead email address) and still get their results.
When this happens, you will receive an integration error notification email from LeadQuizzes informing you that there is no email provided for your most recent lead (because they skipped your Form Fields), as such this lead will not be recorded in your CRM/EMS.
Finally, to stop getting this integration error notification emails from LeadQuizzes, simply ensure that your Form that contains the Email Field (which is required for the integration to work) has the Skip option disabled.