This is the 12068th most frequent Polish word.
listowej
"Listowej" is the feminine singular genitive or locative form of "listowy," meaning "of a letter" or "pertaining to a letter."
Here, 'listowa' is an adjective describing 'poczta', signifying that it pertains to letters.
Poczta listowa dostarczyła list dzisiaj rano.
The postal service delivered the letter this morning.
Here, 'listowa' modifies 'wymiana', indicating that the exchange is related to letters.
Listowa wymiana informacji była kiedyś bardzo popularna.
Letter correspondence was once very popular.
Here, 'listowej' describes 'korespondencji', showing that it is related to letters.