Methods for updating presence information between a first user equipment
(UE) and a second UE over a communications network are presented
including: on an INVITE message delivery failure to the second UE from
the first UE, sending a first PUBLISH message on behalf of the second UE
to a presence server by a communications server; sending a NOTIFY message
to the first UE by the presence server; and setting a current presence
status of the second UE to UNAVAILABLE. In some embodiments, methods
further include: if an immediately previous presence status of the second
UE is set to AVAILABLE, sending a NOTIFY message to all watchers of the
second UE to indicate the current presence status of the second UE. In
some embodiments, the first PUBLISH message utilizes a user-agent header
to indicate that the communications server originated the first PUBLISH
message.