Use SuppressionList to filter your leads against large lists of allowed or disallowed values.
For this example we'll be filtering to ensure that each lead's postal code is contained in a list of allowed values. First, create and populate the list in SuppressionList:
Next, edit your LeadConduit flow to add a SuppressionList enhancement step. Select the "SuppressionList Query Item" from the Enhancements menu:
The enhancement will automatically add a filter to your flow to reject ZIPs not found on your SuppressionList. Simply update the failure response you'd like to deliver back to your lead source.