Abstract: A round trip envelope with front and back faces for writing the outgoing and return addresses, and which enables sealing for both of outgoing mail and return mail sealing flap, which can prevent erroneous postmarking of a stamp. An outgoing stamp affixing area and address writing area are on the front face of the envelope body, and a return stamp affixing area and a return address writing area on the back face. An adhesive area for sealing a sealing flap in a blank area on the back face, in a vicinity of an opening. A distal end portion of the sealing flap extending beyond the adhesive area constitutes a return-mail sealing flap.

Abstract: A round trip envelope with front and back faces for writing the outgoing and return addresses, and which enables sealing for both of outgoing mail and return mail sealing flap, which can prevent erroneous postmarking of a stamp. An outgoing stamp affixing area and address writing area are on the front face of the envelope body, and a return stamp affixing area and a return address writing area on the back face. An adhesive area for sealing a sealing flap in a blank area on the back face, in a vicinity of an opening. A distal end portion of the sealing flap extending beyond the adhesive area constitutes a return-mail sealing flap.