Postfix Problem?

[Johannes Kehrer]

Hello,
I have a weird  problem on my Kolab 3.0 on OpenSUSE 12.3 (Kolab 3.0 is the 
STABLE version there).
When I send an email with Thunderbird or KMail TO the Kolabserver from the 
same account this email is sent, then I get the following error message:

"<johannes at kehrer.cc>: Recipient address rejected: User unknown in virtual 
alias table".

When I send from GMX.DE, or an Exchange Server, everything works correct. 
Also, when I use the Webmailer from this account it works.

Any ideas?

Thanks,
Johannes