You can communicate only with users in the same environment you are working in. For example, if you are working in the TSO/E environment, you cannot use MVS™ facilities to send a message to a user working in the shell.

Shell users who want to exchange messages with other shell users at the same system can use shell commands. Other users may prefer to use TSO/E facilities, in order to be able to exchange messages with all TSO/E users, not just those using the shell.

Alternatively, you can switch into your TSO/E session and send messages to any TSO/E user by using TSO/E facilities, through the OFFICE option of the Information Center Facility (ICF), if it is installed on your system, or through TSO/E commands. You can also receive messages using TSO/E.

If your system has Transmission Control Protocol/Internet Protocol (TCP/IP) or other network management facilities installed, you can log in to the TCP/IP network and send messages to users at other systems.

If your system has UUCP (UNIX-to-UNIX Copy Program) installed and set up, you can use this facility to send files to, or run commands or custom applications at, other sites in the UUCP network.