@mikedev more generally, there are a lot of conceptual issues with AS2 Collection in both data model and protocol. it seems especially problematic to say that a conversation/thread *is* a Collection, because a Collection can be anything -- someone's followers, a conversation, a photo album, an audience, a feed, a task list, and so on. imo this is a fundamental error in information modeling. a Collection ought to represent a set, not myriad other entities that might *have* a Collection.