Shayari Bazar

ITS A 7 LETTER WORD.IF WE REMOVE 1 LETTER FROM IT, IT REMAINS SAME.IF WE REMOVE 2 LETTERS FROM IT, IT REMAINS SAME.IF WE REMOVE 3 LETTERS FROM IT, IT REMAINS SAME.IF WE REMOVE ALL THE LETTERS FROM IT, STILL IT REMAINS SAME.WHAT is IT ?Ans: POSTBOX