
MAPI 191
Subscriber-to-subscriber messages also provide extra functionality for the message sender.
The vast majority of the time (we later cover a few cases in which this is different), the
message sender can mark the sub-to-sub message for future delivery, for private delivery,
and can include a return receipt.
Subscriber-to-subscriber messaging can come into effect in a couple of different ways: The
caller has called Unity, signed into the voice-mail box, and begins message addressing; or
the caller calls another Unity subscriber, that subscriber’s phone forwards the call to the
Unity server (assuming that the telephone system integration method ...