Reusable envelope with pre-cut closure flap, method and machine for manufaturing such an envelope

An envelope comprising an opening and a closure flap to close the opening, the closure flap being foldable down on to a first wall of the envelope and comprising on an inner face a first adhesive layer protected by protection means a second adhesive layer protected by protection means and separated from the first adhesive layer by a separation space, the flap being pre-cut by a first and a second weakening line in the separation space characterised by the fact that the protection means consists of a sheet extending over both adhesive layers the sheet comprising a third weakening line aligned with the first weakening line and a fourth weakening line aligned with the second weakening line.