[Dovecot] rawlog without setting home in userdb

[Claus]

Hi all,

in my settup i decided to set mail_home in 10-mail.conf,
and let dovecot do the hashing to a 2-level directory structure.

mail_location = mdbox:~/mdbox:ALT=/altstorage/%h/mdbox
mail_home = /vmail/%1Mu/%2.1Mu/%u

In my userdb ist homedirectory not set and everythink works as expected,
except when i use rawlog i get only logs in ~/dovecot.rawlog if home is 
set in userdb.
In wiki http://wiki2.dovecot.org/Debugging/Rawlog
it reads:

If you don't have the home directory and you can't or don't want to 
modify userdb configuration, you can add:
mail_home = /home/%u
# or temporarily even e.g. mail_home = /tmp/temp-home


Can you tell me, if my problem is the hashing-configuration or anything 
else?

Claus