Within the office, users must be connected via ethernet. Internally, the mail server is internal.mycompany.com. Externally, it's external.mycompany.com. 

When the user is connected to the internal network, only internal.mycompany.com is reachable. external.mycompany.com is not. When working remotely, the opposite is in effect. (I don't know why this is the case, I'm just the support grunt). 

When attempting to configure Outlook 2011 and the user is connected to the internal network, auto discover seems to try and access external.mycompany.com rather than internal.mycompany.com.

No matter if I allow or deny the request, eventually Outlook will prompt for me to enter the server address manually. When I add internal.mycompany.com, it connects. When the user goes offsite, it switches to external.mycompany.com.

But, when the user comes back to the office, Outlook fails to switch and the user cannot connect.

Apple Mail does detect the correct server details for both internal and external servers, avoiding the issue. 

Can anyone shed any light on the issue? At first, I thought it might have been an Exchange-related issue but as I can get mail to work within Apple Mail, I'm leaning towards an Outlook 2011 issue. 

Is it possible to manually specify both internal and external servers and turn auto discovery off?