DeleGate is a multi-purpose application level gateway, or a proxy server which runs on multiple platforms (Unix, Windows, MacOS X and OS/2). DeleGate mediates communication of various protocols (HTTP, FTP, NNTP, SMTP, POP, IMAP, LDAP, Telnet, SOCKS, DNS, etc.), applying cache and conversion for mediated data, controlling access from clients and routing toward servers. It translates protocols between clients and servers, applying SSL(TLS) to arbitrary protocols, converting between IPv4 and IPv6, merging several servers into a single server view with aliasing and filtering. Born as a tiny proxy for Gopher in March 1994, it has steadily grown into a general purpose proxy server. Besides being a proxy, DeleGate can be used as a simple origin server for some protocols (HTTP, FTP and NNTP).
The license of this software is Freeware, you can free download and free use this proxy software.