[Dovecot] dovecot auth using passwd-file

[Brad]

Im a dovecot newbie and need a little help with the passwd-like file
auth mechanism in dovecot

I got dovecot to work fine with regular /etc/passwd file auth .. so I
wanted to start using another authentication store for virtual users.

So .. I created a /etc/dovecot-passdb file and plopped in an encrypted
password using md5crypt.

Here are the appropriate lines from the dovecot.conf file

auth_userdb = passwd-file /etc/dovecot-passdb
auth_passdb = pam

and here is the /etc/pam.d/dovecot file
#%PAM-1.0
auth       required     pam_nologin.so
auth       required     pam_stack.so service=system-auth
account    required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth


So far .. no dice.  Dovecot reports constant authentication failures.  I
fear that the dovecot-passdb file is wonky.  Can anyone give me any
pointers ?