There’s a bit of a mystery as the U.S. Postal Service’s lease with Johnson City for the Main Street post office is expiring in one year, and city leaders say they haven’t heard from anyone at the post office.Assistant city manager Charlie Stahl says he sent a letter to the post office a year ago reminding them than the 50-year lease expires in 2023. The lease was first signed in 1973 and had options for renewal at set prices, but those renewals are no longer in effect.