From Longman Dictionary of Contemporary Englishmailbagmail‧bag /ˈmeɪlbæɡ/ noun [countable] 1 TCMa large strong bag used for carrying mail on trains etc2 American EnglishTCM a bag used to deliver letters to people’s houses SYN postbag British English
Examples from the Corpus
mailbag• There, wearing his mailbag and leaning over her desk, was Harold Newland, the postman.• Indeed, my mailbag suggests part of the buyer bullying in recent years has been in the smaller multiple ranks.• Slamming her feet down angrily, she made for the mailbags.• The mailbag and telephone line brought many criticisms.• When their mailbags are bulging with outraged voters, they respond. 