A method is provided for mobile transmission of data, especially a method for transmitting multimedia data to a mobile subscriber terminal, wherein the data MM from an MMS application is transmitted to a network unit MMS Proxy/Relay A, the data is re-transmitted to a network unit MMS Proxy/Relay B via a link to a network unit, whereupon it is sent to a recipient, the conversion of the data occurring in a network unit MMS Proxy/Relay between a binary and a textual representation. Elements of data containing an unknown codeword are transmitted in a marked manner in order to provide a method for mobile transmission of multimedia data, a computer program product and a computer program system wherein unknown codes also can be processed without system-related transmission problems, particularly in a forward-compatible manner.