From WordNet (r) 2.0 (August 2003) [wn]:
mailbox
n 1: a private box for delivery of mail [syn: letter box]
2: public box for deposit of mail [syn: postbox, {letter
box}]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
mailbox \mail"box`\ n.
1. A public box for deposit of mail, where it is later picked
up by the postal authority for delivery.
Syn: postbox, letter box.
[WordNet 1.5]
2. A private box to recieve delivery of mail. The term is
used both for boxes receiving mail delivered by the public
postal authority, or by a private services, such as for
mail to employees in large corporations.
Syn: letter box.
[WordNet 1.5 +PJC]
3. (Computers) A location within a computer storage device
where electronic mail is held until it is retrieved by the
addressee. Creation and use of an electronic mailbox
requires special software as well as a data storage
device.
[PJC]
From The Free On-line Dictionary of Computing (19 Sep 2003) [foldoc]:
mailbox
1. <messaging> A file belonging to a particular user on a
particular computer in which received electronic mail
messages are stored ready for the user to read them. A
mailbox may be just an electronic mail address to which
messages are sent and may not actually correspond to a file if
the messages are processed automatically, e.g. a mail server
or mailing list.
2. <programming> A destination for interprocess messages in a
message passing system. A mailbox is a message queue,
usually stored in the memory of the processor on which the
receiving process is running. Primitives are provided for
sending a message to a named mailbox and for reading messages
from a mailbox.
(1994-10-20)