The post office building was designed by Filipino architect Juan Marcos de Guzman Arellano and built in neoclassical architecture in 1926. It was severely damaged in World War II, and rebuilt in 1946 preserving most of its original design.
Daniel Burnham's proposal of the Post Office Building at its current location was due to two reasons: (1) the Pasig River provides an easy means of transporting mails, and (2) lying at the south end of the Taft Avenue axis, it is accessible on all sides, i.e., from the direction of Quiapo, Binondo, Malate and Ermita.
This impressive Graeco-Roman building was designed by Juan Arellano. Built in 1926 in the amount of one million pesos, it was considered as Arellano's magnum opus. A stately-looking building, its design is a perfect example of classic planning employing axial asymmetry and the classical Ionic order including the mouldings and ornaments.
Manila Central Post Office Wikipedia Entry
The Imperial Tapestry: American Colonial Architecture in the Philippines
by Norma I. Alarcon, Fuap, page 141