Abstract: An envelope having front and rear faces which are joined to form a pocket defined by an opening between respective upper edges of the front and rear faces. A flap is joined to the upper edge of the front face and may be folded to overlap a portion of the rear face. An adhesive region is provided on an inner face of the flap, with a line of weakness extending across the adhesive region. When the envelope is first used, only that portion of the adhesive region above the line of weakness is used to fix the flap to the rear face. The addressee opens the envelope by tearing the flap along the line of weakness. The opened envelope can then be reused, with that portion of the adhesive region beneath the line of weakness being used to again fix the flap to the rear face.