post·bag 
/ˈpoʊstˌbæg/ noun
plural post·bags /ˈpoʊstˌbæg/ noun Brit 1 [count] : mailbag 2 [singular] : the total number of letters received by a person, business, or organization at a particular time
▪ We received a huge postbag on the spelling mistakes in our newsletter.
▪ We received a huge postbag on the spelling mistakes in our newsletter.
