A method for sending a message from one host (16) to at least one other host, both of which are attached to a hardware subsystem (12) that is bidirectionally coupled to a mass data storage unit (14) includes (a) transferring a Send Message command through a channel (18) from a first attached host to the hardware subsystem, the Send Message command having at least one second attached host as an intended recipient; (b) buffering (20) at least a message payload portion of the Send Message command at the hardware subsystem and generating an unsolicited interrupt in the at least one second attached host; and (c) in response to the unsolicited interrupt, transferring a Request Message command through a channel from the at least one second attached host to the hardware subsystem for obtaining at least the message payload portion buffered at the hardware subsystem. The Send Message command may be a point-to-point message having a single other attached host as an intended recipient, or it may be a point-to-multipoint message having a plurality of other attached hosts as intended recipients. The hardware subsystem need have no knowledge of the message contents sent between hosts.