[Dovecot] BestPractice to migrate imap mailbox from one machine to another

[Tobias Hachmer]

Hi list,

currently I use dovecot v1.2.15 with maildir++ mailboxes. (Debian 
Squeeze)
I want to set up a different server with dovecot v2, also maildir++ 
mailboxes. (also Debian Squeeze)

What is the best way to copy the existing mailboxes from the older 
machine running dovecot v1.2.15 to the new naked machine?

Greetz, Tobias