Post box 520) is a 1969 Indian Tamil-language comedy film directed by T. N. Balu and produced by N. Vasudeva Menon.

[1] The film stars Sivaji Ganesan, B. Saroja Devi, M. N. Nambiar and Nagesh.

[2][3] Prabhu is the Chennai Manager in a baby food company whose head office at Madurai.

There starts the story of him chasing the letter and he getting messed up with conspiracy by villains and finally coming out of all his problems.

[4] The Indian Express wrote, "Stringing together a few incidents, interesting in themselves but violating logic does not guarantee good entertainment, let alone make a novel movie.