[Kroupware] alias question

[Wim Bakker]

Hello,

I have problems with aliases in kolab so:

I have a user called wim , this user has an 
alias wim.bakker, this means that mail for either
wim or wim.bakker at the domain should be 
transported to the mailbox of the user wim.
Now someone on this list suggested that
this alias is in the virtual file with all the rest
of the users. 
When I look in the virtual file I see some users
defined , but not all, though mail for those users
not in the virtual file allso gets delivered, so I
reckon , the virtual file is not really used. 
My question , where do the users get stored, how
get aliases stored and where in which file can I
check that because aliases don't work allways.
I have a test system running at a customer, with 
9 users, all of them have a username and a alias,
8 of those aliases get mail delivered at the username
mailbox , but 1 gets the error message "alias at domain unknown , bounced".
Allso , when I change the alias of one of the other users
suddenly it gets the same error message.
When I open the webinterface to view the settings
all is there , but one way or another , it doesn't get
updated in....? where?

TIA
Wim bakker