Kmail message storage folders

I currently have Kmail on my server, with thousands of messages in Maildir format on a separate partition (which simplifies migration/upgrading).

They're sorted into many subfolders such as 'cars', 'accounts', 'kde' etc.

I typically ssh into the server from whichever laptop I'm using and run Kmail on the server via ssh, which avoids any syncing issues. However this does mean my server is running for hours just for emails, which costs power.

I'm considering running kmail on a laptop and syncing every few days by copying the new emails to the server's partition using 'cp' or Nautilus or similar to copy recursively only new mailfiles. Can anyone confirm if this will work? Is there a better way to sync?

One possible snag I can see is that kmail has created, in each folder such as 'cars', subfolders called 'cur', 'new' and 'tmp'. Typically 'tmp' is empty but both 'cur' and 'new' are full of messages. How does kmail (or akonadi?) assign messages to 'cur' or 'new'? If it arbitrarily shifts messages from one to the other then my copying idea will likely result in numerous duplicate messages.

I've tried the Kmail documentation but it doesn't seem to throw any light on this.

Chris