If you are trying to configure Outlook Anywhere to route via ARR sever on IIS 7 then you will not be able to connect and you should get error “outlook unable to connect to the Exchange sever.”

in IIS logs you should find the error code 404.13 (which mean content length is too large)

Solution:

By Default IIS ‘Maximum allow content length’ is set to 30 MB. We just have to reset it to 2 GB(2147483648 byes).

To configure this select the required website and double click  on ‘Request Filtering’

Select ‘Headers’ tab and click on ‘Edit Feature Settings’ then increase the ‘Maximum allow content length’ to 1 GB (1073741824 bytes)