Show a form to new visitors
You need to admit that it's frustrating when you enter a page, where you have already provided your email address, and there are forms/pop-ups showing asking for this particular information again. Spare your users this frustration and create an action path to show a specific form only to a targeted audience.
Let's start from Trigger:Page Visit, which means that if somebody visits your page (leave the "configure" section empty) and if there is no email address in the database, which we apply through Filters: Email → unknown, means that this person will see a specific form. Drop Action: Show a form and add an appropriate form from the list.
Now, everybody who hasn't given the email address will see the form.