I’ve backed up all my email and went ahead to copy it to another IMAP server. After about 2 hours I got an error message: “Cannot send command to the server because the response for previous one was not received”. Below were several lines of information like:
Not enough data in a stream
There were more like these.
I gave it a rest and tried the day after. Still got the same error messages.
I noticed there were some email messages copied to the server I am trying to migrate to, but definitely not all of them.