Hi, @wilbert. If you want an ability to use the same email address to subscribe multiple times, you should try integration with our Newsletters plugin.
It allows to subscribe using the same email address as many times as you want. Just install required plugin and choose it in Subscribe options of required popup: http://prntscr.com/jgi049
Also, I have a different solution for you – you can create Mailchimp account and use it to collect subscribers. All you need – register Mailchimp account and create as many different subscribe lists as you need. Then you can set different subscribe list for each popup on your website.
This way you can collect subscribers with the same email address in different subscribe lists.