@baris OK. I made an issue on nodebb github see(https://github.com/NodeBB/NodeBB/issues/7770).
Thanks for your answer !
We are getting a lot of registrations done through invalid email addresses.
All the registrations are coming from different ip addresses. Of-course we can select and ban the users, but the question is HOW LONG?
One solution can be using captcha for registration, but unfortunately there is no plugin for this!
Do let me know how to stop this?
using this plugin: https://community.nodebb.org/topic/2187/question-and-answer-plugin-for-the-registration-form