CANT access sock5 proxy server on pop port(110)

Detail:

1. I setup a sockd proxy on port 110 on a public server.
2. My win2k3(client) cant connect this sock5 proxy. no response anyhow.
3. My win2k3 can send and receive email from other public pop3 server. So it
have accessbility on port 110.
4. My other WinXP under same LAN network can access this proxy without
problem. So its not about nat.
5. I check and tried disable the IPSec on wi2k3 or set it on Client mode.
Which mean permit any IP and ICMP connection. But problem still.
6. I check the TCP/IP advance setting of network connection on my Win2k3.
the firewall is off. And I have no other firewall at all.

Is there any one have any idea where should I put hand on?

Thanks
Tomasen