This is the 8403rd most frequent Polish word.
pocztowy
"Relating to mail or postal services."
The word 'pocztowy' is used as an adjective to describe an office related to postal services, indicating its connection to 'poczta' (post).
Urząd pocztowy znajduje się blisko mojego domu.
The post office is located near my house.
Here 'pocztowy' modifies 'skrzynka', meaning 'post box' to indicate what type of box it is, specifically for mail handling.
Kupiłem skrzynkę pocztową na listy.
I bought a mailbox for letters.
In this context, 'pocztowy' is used to specify the type of code, directly attributing it to postal purposes (postal code).