Which preposition to use with mailbox

at Occurrences 1%

She bore some eight or nine letters in one hand, and fanned herself with them in a leisurely flat-footed progress to the mailbox at the lower corner.

in Occurrences 1%

Blanche Devine spied them from her sitting-room window, and she made the excuse of looking in her mailbox in order to go to the door.

on Occurrences 1%

In every district there was a mailbox on the fence of the chefferie, the chief's office, and on the trees alongside the road at regular intervals, and the driver took mails from people who hailed him.

Which preposition to use with  mailbox