This proxy helps Thunderbird use MSN POP3/SMTP servers. Thunderbird needs help because MSN requires its own Authentication type. Feel free to try the proxy with other mail clients, but don't be surprised if it doesn't work.
To use:
I use sockets asynchronously (a Windows extension to standard sockets). It may be more straight forward to create a multithreaded program and use blocking sockets, but I fancy asynchronous sockets.
While the main proxy program is tightly bound to Windows, all Windows specific code is confined to a single file. This file implements a generic TCP proxy.
All code specific to POP3, SMTP, NTLM Authentication (a.k.a. MSN Authentication) is fairly straight forward. Anyone wishing to make a port will have an easy time of it. Here is my guess as to what will be required: