郵便ゆうびん私書ししょはこじゃなかったです
yūbinshishowa kojanakattadesu

Noun
Desu Copula

The polite, past negative form of 郵便私書箱

1. It wasn't a PO box.; It wasn't a private mailbox.

Past/Perfective
Negative
Polite
Casual Register