i managed to find it out myself. rather simple error in the end it seemed. the right auth combination to use is passwd / pam although that doesn't show any where. thus in order to get dovecot to work everything you have do to is download it, configure it (standard), make / make install and then finally edit the conf according to your needs and for "simple" authentication set auth_userdb to "passwd" and auth_passdb to "pam login".
it makes a very nice imap server thus far. much faster than for example courier-imap.
