A collaboration system using peer-to-multi-peer distribution of messages representing changes to a shared workspace. Each peer determines a distribution mechanism for messages to each of the target peers sharing the workspace. The selected distribution mechanism may depend on capabilities of a home relay associated with a peer initiating a message. Further, messages to subsets of the target peers sharing the workspace may be distributed using a session for each subset on which each message is sent only one time. The subset of target peers associated with some of the sessions may be selected so that target peers for which communication attempts have failed are grouped in the same session. In some scenarios, the initiating peer may provide multiple routing paths for target peers in a session and the home relay server may appropriately forward the message to the target peers, using one of the routing paths.