[Dovecot] cas proxy ticket as password

Hi everybody. Hi I'm tryingto use CAS for authenticating in dovecot. I have installed pam_cas and when I try castest i get "cas:authenticationSuccess" for my service (imaps://mywebmail.com) But when I actually try to login, dovecot uses the PT from the cas server as password. Any ideas what I'm missing? Thanks a lot.