There seems to be a lot of interest in sync related protocols in this thread and dismissal of JMAP as a result. This is bad, because the current state if synchronization protocols still kinda sucks - full disclosure, I work on <a href="http:&#x2F;&#x2F;GitHub.com&#x2F;amark&#x2F;gun" rel="nofollow">http:&#x2F;&#x2F;GitHub.com&#x2F;amark&#x2F;gun</a> which is a JavaScript based syncing database. Getting synch right in p2p or federated systems (email) entails more detail than centralized ones. So any work on synchronization should be seen as favorable compared to how bad other protocols are for sync.