The invention relates to a method and a device for modifying modular messages (7) that can be transmitted via an electronic message transmission system using an electronic arithmetic unit, in particular a computer. A message (7) is read using a read device (6) and the structure (10) of the read message (7) is determined. An individual structural unit of said message (7) and modifications that canbe carried out to the selected structural unit are then determined. The possible modifications and/or functions are then displayed and a modification and/or function that is to be carried out is/are read. The validity of the selected modification of the individual structural unit is verified with regard to the structure (10) of the message (7). If the modification is valid, it is executed and a modified, new message is issued.