Abstract: Disclosed herein is a foldable, one-piece mailer having at least one portion thereof that may be easily detached and retained by a recipient. The mailer comprises a sheet having a front side for placing postage and indicating the recipient's address, and a back side that includes space for printing text to the recipient. On the back side of the mailer appears a means for visibly indicating sections of the mailer that are intended to be folded for mailing. Such means may include dotted lines, pre-formed creases, or any other indicator that delineates the sections that should be folded by a user to form the mailer into a shape resembling an envelope. The detachable portion of the mailer is removably secured to the mailer so that it can be removed by the recipient and retained. Methods for collecting information pertaining to the manufacture and sale of said mailers are also disclosed.