Hi Jonathan (@user5f15f943c6034976),
Since you want to still allow the user to submit the form, how about showing an HTML field with your rejection message via conditional logic if one of your 100 small towns is entered?
Populate Anything makes this a breeze. It doesn’t support json/csv files so you’ll need to either import the data as a custom table in your WordPress database - or - just use Gravity Forms itself as a simple database.
Once you have the data accessible to Populate Anything, you could create a Hidden field whose value is dynamically populated based on the value of another field. You could label this field “Is small town?” When the user enters their town, you can filter the value of this Hidden field to return a true or false depending on whether the town name exists in your list of small towns.
Here’s an example of what that field might look like if you use a Gravity Form to store your small town list:
Then, you can show/hide your HTML field based on the value of this “Is small town?” field.