-18597 (403) connecting Outlook Mac 2011 to Exchange 2010 SP3

Hello, I have a problem with my new Mac. I am trying to configure my exchange mailbox on my Mac but I keep getting the same error.

This is what I have done:

- configured Apple Mail to our exchange server settings (this works; the email, calender etc is retrieved)

- access the OWA via the internal .local domain and the external URL (this works)

- tried to use the Microsoft Remote Connectivity Analyzer and using our OWA url this all works fine (I cant test the .local url since this is an internal domain)

- configure the server address (the .local domain) in outlook and this doesnt work. I keep getting the -18597 error.

- I have turned on outlook error logging and this displays a 403 error

We use exchange 2010 SP3 and Mac office 2011.

I find it very strange that OWA works, Apple mail works but outlook doesnt

I have read many posts before on using a different NTP time server and changing the computer name of my Mac but this didnt work.

Anyone any idea?

Thanks, Bart