3.2.6.2 Server or List Restoration
If a protocol server restores data from backups then protocol
clients might not be able to determine the correct state of the items. Protocol
clients SHOULD discard their local data because the protocol server might have
been restored to undo changes that protocol clients still have. Protocol
clients can keep a backup of changes that were not uploaded to the protocol
server. A protocol server or list restoration event is indicated by Changes.Id.ChangeType="restore"
and no data
in the Changes.Id listed in section 3.1.4.7.1.1.