UK, [US and ANZ] mail [noun] [U] - the number of letters received at one time or on one subject We've had a huge postbag on the subject of animal rights.It was clear from our postbag that viewers were unhappy about the programme.A postbag is also a mailbag.
POSTBAG
Meaning of POSTBAG in English
Cambridge English vocab. Кембриджский английский словарь. 2012