Hi,
I checked our Exchange-Server settings and they used autodiscover. Unfortunately it submitted the internal server for intern and extern use. I chaged it with our ITs and it works perfectly now.
Still Apple should allow users to "switch off" autodiscover or just allow them to set the server settings manually.
This is the way how to configure the Exchangeserver:
Use on the Exchange Server Shell the command: Get-WebServicesVirtualDirectory |fl identity,internalurl,externalurl
and check the server settings. You need to start the shell as an administrator.
If the entries are wrong change them using these instructions:
http://premnair.wordpress.com/2010/07/03/configure-ews-autodiscover-owa-oab-ecp- on-exchange-server-2010/
Thanks to subsriram. That was the right hint!!!!
And please Apple follow my above suggestion.
Cheers,
zarrsten