INT 21 - LANtastic - GET MESSAGE PROCESSING FLAGS
        AX = 5F9Ah
Return: CF clear if successful
            DL = bits describing processing for received unsolicited messages
                bit 0: beep before message is delivered
                bit 1: deliver message to message service
                bit 2: pop up message automatically (v3+)
        CF set on error
            AX = error code
SeeAlso: AX=5F9Bh,AX=5F9Ch,AX=5F9Dh

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