Whoever, being a Postal Service officer or employee, unlawfully secretes, destroys, detains, delays, or opens any letter, postal card, package, bag, or mail entrusted to him or which shall come into his possession, and which was intended to be conveyed by mail, or carried or delivered by any carrier or other employee of the Postal Service, or forwarded through or delivered from any post office or station thereof established by authority of the Postmaster General or the Postal Service, shall be fined under this title or imprisoned not more than five years, or both.