This is what _passwd_hook_default_username is for.

Application: Horde is running as webmail server and users should be 
able to change their password. Mail server supports multiple domains, 
Horde/IMP are used as web frontend. Authentication is done by LDAP.

Problem: Passwd changes username@domain.de to username, obviously ldap 
access fails then.



Solution: In main.php there are two locations with a line like

$userid = Auth::getBareAuth();

I changed that to

$userid = Auth::getAuth();

which solved that problem for my application. I know that is a quick'n 
dirty solution. One more line in config.php would be the correct 
solution, so admin can select the preferred way to present the 
username. Please consider that for next version of Passwd.

cheers

Christian