[Samba] pam_smbpass.so

[Thomas Angst]

Howdy folks,

I can authenticate postfix via sasl-pam.
But if I would like to use the smbpasswd file with pam_smbpass.so it is 
not working.
The strange thing is, sshd and cyrus imapd is working with pam_smbpass.so

I get this entry in /var/log/messages:
Nov  2 17:05:04 thomas PAM_smbpass[3885]: Failed to find entry for user 
bubu.

/etc/pam.d/smtp:
auth required pam_permit.so    # is working
auth required pam_unix2.so    # is working too
auth    required pam_smbpass.so debug audit nodelay 
smbconf=/etc/samba/smb.conf    # is not working

Is there any known bug, which interacts in this constellation with postfix?
I'm not a C programer so I will have some problems to debug the source 
directly...

greetings
Thomas Angst