Forwaring a std port to RDP-port via RRAS

How do I forward a standard port (eg. 110) to the RDP-port (3389)?
I have managed to forward port 123 to port 3389 via RRAS -> ServerName
-> IP Routing -> NAT/Basic firewall -> Local Area Connection ->
Services and ports
But if I try defining a port forward from eg. 110 to 3389, RRAS
responds with "The specified special port already exists. Enter a
unique special port."
I have no services running on port 110 - how do I make it work?

Make sure your not running POP3 services on your Server
as POP3 uses port 110 to recieve mail.
>-----Original Message-----
>How do I forward a standard port (eg. 110) to the RDP-
port (3389)?
>I have managed to forward port 123 to port 3389 via
RRAS -> ServerName
>-> IP Routing -> NAT/Basic firewall -> Local Area
Connection ->
>Services and ports
>But if I try defining a port forward from eg. 110 to
3389, RRAS
>responds with "The specified special port already
exists. Enter a
>unique special port."
>I have no services running on port 110 - how do I make
it work?
>.
>