The crossword solutions for the term 'ITEM IN A P.O. BOX' are ENV and LTR. ENV stands for envelope, which is a type of paper container used to send documents or other items through the mail. An envelope typically has a flap that is sealed shut with glue or another adhesive. LTR stands for letter, which is a written message sent from one person to another. Letters can be sent through the mail in an envelope, or they can be sent electronically.