What does the word mail mean?

Usage examples for mail

  1. The morning's mail still lay on the table, some letters open, as they had been when the discovery had been announced. – The Dream Doctor by Arthur B. Reeve
  2. Four o'clock was mail time. – The Goody-Naughty Book by Sarah Cory Rippey
  3. How will you mail them? – Six Little Bunkers at Cowboy Jack's by Laura Lee Hope