Você considerou o Outlook Anywhere ?
For remote connections, Outlook offers Outlook Anywhere, an alternative to VPN connections that allows you to use Outlook just as you normally do at your organization, without the need for any special connections or hardware, such as smart cards and security tokens. Outlook can connect to Exchange through the Internet by using remote procedure call (RPC) over HTTP. The Outlook Anywhere feature allows you to access your Exchange account remotely from the Internet when you are working outside your organization's firewall.