Ok so here it is. I have a customer who is migrating to teams only from islands mode. Teams only users are able to receive IM messages from islands users sent from Sfb and he then returns them without issue and the islands users recieve the IM in skype. I have been advised this should not be possible. I believe that it is only when the SfB user sends a chat first that makes uninterrupted chat possible.. If the Teams only user was to initiate the conversation it would then seek to land in the islands user's Teams client.... Sorry if this doesnt make sense but is my thinking correct?