Version:           4.2.1 (using KDE 4.2.1)
Installed from:    Gentoo Packages

Sometimes it is really a nightmare to backup kmail's stored mails from my mail accounts: the only thing I see is to copy/paste the folder, but this sometimes does not work properly and thus I *strongly* suggest implementing a easy option to import/export data to a compressed file for example.

It could work that way:

Export:
Create a tar.gz file where user wants containing:
 - the piece of that account(s) config
 - the folder(s) selected to be included (in case user stores mail from each account in a separate maildir)

Import:
Import from a tar.gz
 - the piece of that account config and merging to main kmail's config
 - the folder(s) containing mail data

Please, review this implementation, since I think is what kmail is lacking nowadays (specially due to the rapidly releases of major KDE's version.

Thanks