Tell us what you are trying to do?
A'm looking for a solution to stop spamming in a cred | post Toolset forms which can be fulfilled with no registration (only typing emails from guests in site in it).
I've created a custom role for Users = "Spam" and periodically put some new users in it (with spammers - emails from front-end forms).
Are there any ready Toolset instrument to check & return error from front-end cred | post Toolset before save
Is there any documentation that you are following?
If you are referring to checking if the user's email is on a spam list then no we are not able to do this. This would definitely require some custom code to check the email when the user submits it.