The invention relates to a method for transmitting messages from a user application of a subscriber to a user application of another subscriber with the aid of the Multimedia Messaging Service MMS, the message being in the format of an external application and is identified as such by an application identifier that is transmitted along with the message. According to the invention, the multimedia message service is used by the external application as a transport system for transmitting the message. The message is identified by a network element of the Multimedia Messaging Service using the application identifier and is transmitted in an unmodified state via the Multimedia Messaging Service and forwarded to the external application. The invention also relates to a subscriber terminal and a communication system for carrying out said method.