[Dovecot] dovecot and ldap passwords.

Hallo. First of all I'm sorry for my bad english. I have a question about how dovecot use passwords. I have all my mail accounts in a ldap database. The user password are stored in form: {crypt}mypasswd. In dovecot-ldap.conf I have default_pass_scheme = CRYPT. All is working fine. The problem in the crypt scheme is that I can't have passwords more than 8 characters long. So I've tried to change the type of the ldap passwords in SSHA or SMD5, but in this way the users can't authenticate yourselfs. Dovecot doesn't understand SSHA or SMD5?