[Dovecot] best practice to have sent mail folder on dovecot imap server

I've already asked this here: http://serverfault.com/questions/533940/best-practice-to-have-sent-mail- folder-on-dovecot-imap-server

Hi,

when I add a mail account to KMail (or most other MUA I suppose) the sent mail folder is on the local machine and I don't have my sent mails on other machines.

I'd like to have a sent mail folder in IMAP and I thought that there would already exist a standard or best practice how to set this up so that the mail is only transfered once to the MTA and from the MTA to the IMAP server.

I even thought to remember an RFC related to this problem?

It isn't that simple, is it? I'm using Exim.

Regards, Thomas Koch