Master auth only

Hi,

i'm trying to configure Dovecot proxy with user authentication on
proxy side only, so backends will authenticate using master password
(proxy is configured to send it). The problem is that Dovecot, on
backends, is telling me that i need to configure at least one auth
mechanism:

auth: Fatal: No passdbs specified in configuration file. LOGIN
mechanism needs one

The master auth is correctly configured.

I want to accomplished to have user database only on one place
(=proxy). Any hints?

azur