> The conversion of the Mailbox from Courier to Dovecot will be done with > "courier-dovecot-migrate.pl"-script[1], which works fine. However after > running "courier-dovecot-migrate.pl" the Courier-Files still remain in > the Maildir.
expressed unlucky :-) sure, dovecot doesn't need these files after the migration. I have to test, if it's possible to convert from a previously "courier to dovecot migrated maildir" back to courier-format.