Thanks for reaching out to Jotform Support. Unfortunately, our Italian Support agents are busy helping other Jotform users at the moment. I'll try to help you in English using Google Translate, but you can reply in whichever language you feel comfortable using. Or, if you'd rather have support in Italian, let us know and we can have them do that. But, keep in mind that you'd have to wait until they're available again.
Now, let me help you with your question. If I understand you correctly, you wanted to send out a form to 15,000 form fillers? If so, if you are expecting that number of submission entries I recommend subscribing to our Enterprise plan because the account usage and limits are unlimited.
You can also check our Pricing page for a quick breakdown of the plans that Jotform offer and its feature. If you’re interested in Jotform Enterprise, our dedicated Enterprise Sales Team can help you and answer any questions that you have. You can contact them here. Please fill out and submit the Jotform Enterprise Sales Contact Request and someone from our Enterprise Sales Team will get back to you shortly.