The building runs through the block to East 24th Street, where there are loading docks and another much smaller and less formal public entrance.

[2] It is a two to three story building clad on its main facade with polished "Dakota Mahogany" granite in the Classical Revival style.

The main facade features six two-story Doric order piers and pilaster that surround the recessed entrance bays.

The exterior also features five bronze relief sculptures by artists Edmond Amateis and Louis Slobodkin illustrating different forms of communication: from west to east, the god Mercury, jungle drums, mail, carrier pigeon, and smoke signals.

The plan involved using flying boats to transport mail from Floyd Bennett Field to a new seaplane base on East 23rd Street that was being constructed nearby.