Abstract: A panelled mailing bag with zippered opening and a spaced two-part address card mounting pocket on a panel thereof with a card so received therein that the mid portion is exposed to receive postage and enable ready cancellation thereof. The card is apertured for securement by seal means to the zipper slide and eyeletted patches on the bag panels whereby the slide is maintained in closed locked position and unauthorized access to the bag is prevented without leaving overt evidence.