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

A method for manufacturing an envelope, the method comprising:

• forming a closure flap in a wall of the envelope;
• placing two adhesive layers on the closure flap that extend parallel to each other and are separated from each other by a separation space;
• placing a sheet on the two adhesive layers to form a protection means;
• forming a first weakening line in the separation space on the closure flap and a third weakening line in the sheet, wherein the first weakening line and the third weakening line are formed together such that the first weakening line is aligned with the third weakening line;
• forming a second weakening line in the separation space on the closure flap and a fourth weakening line in the sheet, wherein the second weakening line and the fourth weakening line are formed together such that the second weakening line is aligned with the fourth weakening line;
• and
• wherein the first weakening line and the fourth weakening line are spaced apart and extend parallel to each other in the separation space.