Enter a clue or pattern or both:
The Clue
Mail: Abbr. (4 letter answer)
The Answer
LTRS
Tags
Notes
The answer LTRS is seen occasionally, appearing about once every 850 puzzles.
Related Clues
Alphabet: Abbr.
G.P.O. items
P.O. boxful
P.O. items
Posts: Abbr.
U.S.P.S. deliveries
Posted pieces: Abbr.
U.S.P.S. cargo: Abbr.
What P.O.'s handle
Contents of many files: Abbr.