Crossword Puzzle Post Office goal

Clue: Post Office goal

Drops in a post office slot (MAILS with 5 letters)
Post-office purchases (STAMPS with 6 letters)
Post office item (MAILER with 6 letters)
MD office posting (HRS with 3 letters)
Where goal posts are (ENDZONES with 8 letters)
Post office activity, or a hint to this puzzle's theme (LETTERSORTING with 13 letters)
Post office department (GENERALDELIVERY with 15 letters)
Post Office devices (DATERS with 6 letters)
Post Office motto word (NOR with 3 letters)
Object of playing post-office (LIPSERVICE with 10 letters)