Abstract: A specialized mailing instrument having an envelope portion and a cover portion adapted to overlie the envelope portion in a folded condition. The exterior of the cover has a space for addressee information and the reverse side has space for return information. Transfer means such as carbon contact paper, underlies the addressee panel so that information impressed on the addressee panel, including recipient acknowledgments, if requested by the sender, is transferred to the envelope portion and the enclosed document for verification. The cover is perforated for removal upon receipt and foldable with the return address showing for return and verification to the sender. A security window may be provided to permit inspection of the contents of the envelope. The instrument may be partially pre-printed for large volume users and may include a detachable notice of attempted mail delivery. The instrument is also suitably provided with identifying distinctive markings and appropriate instruction as to use.