Is there a way to add someone to a black list?

Hello is there a way to enable a black list for email sender? there is a stalker who sent always same messages and i'd like to block his email address to send messages via jotform thanks

Unfortunately, it's not possible to block users based on email address, you may only limit the submissions on your form based on a question, on this case it should be the email address. Here's the guide: https://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question 

You may also provide us the submitter's IP address and we will block it on our end so he cannot access JotForm anymore.