so the email would only be able to submit the form once per...day? hour? week? what would the use case be? If only for spam, then use spam protection like cleantalk.

Thanks for the proposal but it think if can enable the limits per day for example to 1 or 2 per email then will be just great. The users will not get spammed. Will try with Ai.

By the way can you see this :https://old.voxel.guide/snippet/send-fluent-forms-entry-to-post-author/

I can't get it to work to switch to fluent forms....

Yes, you can with FFpro. Check the settings under the single form. Per user, per ip, per day.

Does not have per email though...I am not forcing users to be registered to use the contact form... so a visitor can use it.

will try it once i am able to send the form to post author... currently i am not able....