If you are registered customer
1. Plugin checks if you are a newssubscriber and if YES than plugin doesn't show popup window
if NO than plugin shows popup window.
Please check this logic.
Pay attention to cookies.
I can be a user already registered for the newsletter.
But how does the plugin behave if I access the website without being logged in?
if I access from a new device where the "foxnetsoft.newslettersubscription.popupwindow" cookie does not exist or has already been deleted? The plugin show popup window and I can insert my email...
But I am already registered.. and I receive again a coupon code.
It is importa to check in the newsletter table if my email is already present, and send an email with the notification.