They are closed on Sundays, but.... Perhaps you could call on Saturday, talk to the Supervisor, and ask if the clerk on duty can call you IF they come in. Usually, someone has to be at the post office for an hour or two EVERY DAY because mail usually comes in EVERY DAY, but because they're closed, it isn't delivered until the following workday. Monday (unless Monday is a holiday - Memorial Day) or Tuesday. It's truly out of the ordinary for someone to let you get mail on a off day, but maybe you could work something out w/ your local P.O. Good Luck!