Nginx

Nginx (pronounced "engine x") is an open source reverse proxy server for HTTP, HTTPS, SMTP, POP3, andIMAP protocols, as well as a load balancer, HTTP cache, and a web server (origin server). The nginx project started with a strong focus on high concurrency, high performance and low memory usage. It is licensed under the 2-clause BSD-like license and it runs on Linux, BSD variants, Mac OS X, Solaris, AIX, HP-UX, as well as on other*nix flavors. It also has a proof of concept port for Microsoft Windows.