connection to pop server

[worku2]

I am developing a small project with asp.net c# as a default. this project what will do is taht retriving message and sending message from pop sever .when i am trying with some code the system display the following error.
An I/O Error occured: System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at Jscape.Email.Pop.Connect()
how can i solve this error. thank you.