in ‧ box BrE AmE , in box /ˈɪnbɒks $ -bɑːks/ noun [countable]
1 . the place in a computer email program where new messages arrive:
I had 130 emails in my inbox this morning.
2 . American English a container on an office desk that is used to hold letters, documents etc that you must deal with SYN in tray British English ⇨ ↑ outbox