From version 2.0 you may chose to block form submitting for disable certain notification(s) when user's input match your case.
In form settings:
You will see Blacklist Options section
Default is Block form submitting and you may click to chose Skip notifications. All notifications which added to the form would be listed out.
If the icon before notification name is gray then means the notification would not be skipped even user input match your case.
The above setting means if user's input match any blacklist / white list / email list case which added to filed then the form still can be submitted which Client notification will be skipped.Purchase Gravity Forms Blacklist and Custom Validation Pro