Fresh kolab3 on Debian/Wheezy: local delivery is not staying local?

[Johannes Graumann]

Hello,

The Kolab3 System that is soon to replace my running 2.4 one currently has 
no mx record etc. set.
This makes me suspect that the reason why locally triggered test mails 
(/etc/aliases has "root: me at mydomain.org") are not delivered is that postfix 
is not keeping such mails local but routing them out and they are thus 
currently not received.

Is that accurate? Can that postfix-behavior be changed?

Sincerely, Joh