From Longman Dictionary of Contemporary Englishmailermail‧er /ˈmeɪlə $ -ər/ noun [countable] especially American EnglishTCM a container or envelope used for sending something small by post
Examples from the Corpus
mailer• Even some big mailers are having problems complying with the new rules.• Electronic bulk mailers have ways to disguise their messages that can frustrate even sophisticated filtering software.• Bustamante conceded that he should have told Lockyer about the endorsement before the Senate leader learned of it in a Calderon mailer.• He was slow to start his fundraising efforts and has barely collected enough contributions to send out mailers.• He uncovered medical reports, pharmaceutical mailers, invoices, business letters.• Those with secure mailers can add your certificate against your entry in their address books.• With the fliers were mailers to send to Hayworth.From Longman Business Dictionarymailermail‧er /ˈmeɪlə-ər/ noun [countable]1MARKETING a piece of advertising material designed to be sent by mailThe marketing plan could include sending mailers to likely purchasers.2a person or organization that sends mail, especially in large quantitiesBig corporate mailers try to get discounts from the U.S. Postal Service.3especially American English a container or envelope used for sending something small by mailSYNpostal packet BrE 