You want to setup Outlook Anywhere but ask yourself what is behind that fast and slow networks connection detection?
Exchange Server Technet:
Outlook defines a fast connection as a connection that is faster than 128 kilobits per second (Kbps). Outlook defines a slow connection as a connection that is slower than or equal to 128 Kbps.
Outlook is configured to determine a user’s connection speed by checking the network adapter speed on the user’s computer, as supplied by the operating system. If the reported network adapter speed is 128 KB or lower, the connection is defined as a slow connection.
Additionally, I would like to provide you some RPC over HTTP troubleshooting links: