Crossword Puzzle Post office onslaught

Clue: Post office onslaught

Object of playing post-office (LIPSERVICE with 10 letters)
Post office department (GENERALDELIVERY with 15 letters)
Post office? (STAMPINGGROUNDS with 15 letters)
Post office need (e.g. DATER with 5 letters)
Post office activity, or a hint to this puzzle's theme (LETTERSORTING with 13 letters)
Post-office fixture (FLAGPOLE with 8 letters)
Distributing post offices: abbr. (DPOS with 4 letters)
Post office rental (BOX with 3 letters)
Did post office work (SORTED with 6 letters)
Former Post Office service (SPECIALDELIVERY with 15 letters)