strange problem connecting Outlook 2013 and Kolab 3.4 (ActiveSync)

[Michael Schumacher]

good morning,

I installad the most recent version of Kolab (3.4) on a centos7 server
and everything seems to work fine.
The only problem I am facing is when I try to connect an Outlook2013
client via ActiveSync.

The machine dmzserver1.mydomain.de is part of my private
(192.168.1.xxx) company network, the machine www.mynetwork.de is in
the "public" at a root server provider.

I can login to
http://dmzserver1.mydomain.de/Microsoft-Server-ActiveSync and get the
"it works" response.
I can "nslookup dmzserver1.mydomain.de" successfully in my private
(192.168.1.xxx) network from the windows client.

When I try to setup outlook using this
https://kolabnow.com/clients/outlook#settings-clientconfig-outlook-as
howto, Outlook cannot resolve the IP-address correctly. Instead, it
connects to my webserver www.mydomain.de and complains about an
outdated certificate. The certificate is actually expired.

"nslookup mydomain.de" and "nslookup www.mydomain.de" both resolve to
the public IP-address.

The puzzling thing is that outlook does not seem to resolve the mail
server name correctly to my internal machine dmzserver1.mydomain.de,
it resolves the to the mydomain.de machine instead.

If I try to use the IP-address instead, it cannot find the
Kolab-server at all.


best regards
---
Michael Schumacher