[Dovecot] Virtual and system users

Hi.

I can not understand, how at presence of system users (passdb shadow and userdb passwd) and virtual (for example, user@host.domain.com as system user and user@domain.com as virtual) to allow virtual users to not enter a domain part of username at a login, and to allow system users to use a full name (user@host.domain.com)? I have read the documentation and default config - I can not understand, how it can be made? If the parameter "auth_username_format = %n" worked inside of separate passdb{} and userdb{} sections, it can be realized, but it does not work inside of them :( .

M. Alhimenko.