Your installation may use various security enhancements to customize how the SEND command works. For example, using RACF®, your installation may control which users can send messages to other users. If you send a message to a user that you are not authorized to send messages to, the system cancels your message and displays an informational message on your terminal.

If your installation uses security labels and security checking, when you use the SEND command to send a message, the security label you are logged on with is associated with the message. The security label on the message has an effect on how the intended receiver of the message receives it.

For example, if you use the SEND NOW command, then even though the intended user is logged on and is receiving messages, the user will not receive the message if the user's security label is less than the message's security label. In this case, the system deletes the message and notifies you.

Also, if you use the SEND LOGON command, and the intended user is logged on and is receiving messages, the user will not receive the message if the user's security label is less than the message's security label. In this case, the SEND LOGON request is treated like a SEND SAVE request, and the system stores the message for the user.

With the SEND SAVE command, the system stores the message for the intended user as it does normally. However, because your security label is associated with the stored message, the receiving user will not be able to receive the message later unless the user logs on with a security label equal to or greater than the message's security label. If the receiving user has no such security label defined, the receiving user will never be able to receive your message.

Another point regarding security labels and receiving messages is that the LOGON MAIL command does not display all of your waiting messages if there are mismatches between your security label and the security labels associated with the messages.

Additional security considerations for sending and receiving messages are in Displaying System Messages - LISTBC Command.