Customer: Postal code Optional when filling streetname & housenumber

Hi,

We considered when we fill in the streetname & housenumber while making a new customer the postal code needs to be filled in.

If we leave the streetname & housenumber blank the postal code is optional.

Can we change somewhere the properties?

Note: THIS IS NOT BY CHANGING THE FIELD PROPERTIES IN MASTER LAYOUT (NOT UNCHECKING THE MANDATORY CHECKBOX OF POSTAL CODE) !!!!

Thanks