Crossword Puzzle Office activity

Clue: Office activity

Post office activity, or a hint to this puzzle's theme (LETTERSORTING with 13 letters)
Assayer's activity (TEST with 4 letters)
Post-office item (STAMP with 5 letters)
Final race for office contenders (GENERALELECTION with 15 letters)
Post office hunk? (MAILMODEL with 9 letters)
Corner-office occupant (BOSS with 4 letters)
Key group of officers (CADRE with 5 letters)
First president to get married while in office (TYLER with 5 letters)
Meet activity (SWAP with 4 letters)
Un-p.c. activity (LEERING with 7 letters)