syncFolderUIDRange ErrorConnection on one of the folders

Not in this case.
I did run the moving out all emails (about 5k) from folder to local one, which made Mailspring sync very happy. Moving back all emails by batches (~500 emails at the time) didn’t cause any problems and all emails had been synced.

It is a pitty, but after successful sync, Zimbra // mailspring sync has been triggered and quite a bit of emails disappeared…