A special check on postal codes in Poland is available as of Release 3.0A. If 9 is stored as the checking rule for the postal code in Poland in the Country Field Checks screen, the system checks whether your postal code entry has the NN-NNN (N = number) format.
From the complete Implementation Guide, select Global settings -> Set countries -> Set country-specific checks , and enter 9 as the checking rule and 6 as the length of the postal code for Poland.
For more information see the implementation guides documentation of the work step