Propagate these changes onto the other server: get the corresponding
UIDs from the database, then a/ issue an UID STORE + UID EXPUNGE command
to remove messages that have not already been deleted on both servers,
-and /b issue UID STORE commands to propagate flag updates (send a single
+and b/ issue UID STORE commands to propagate flag updates (send a single
command for each flag list in order the reduce the number of round
trips).
(Conflicts may occur if the metadata of a message has been updated on