A high performance HTTP and reverse proxy server. The Nginx [engine x] software was designed to be an HTTP server and mail proxy server.

Nginx is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Nginx powers several high-visibility sites, such as WordPress, Hulu, Github, Ohloh, SourceForge and TorrentReactor.

Nginx Features:
1. Basic HTTP features:
2. Handling of static files, index files, and autoindexing; open file descriptor cache;
3. Accelerated reverse proxying with caching; simple load balancing and fault tolerance;
4. Accelerated support with caching of remote FastCGI servers; simple load balancing and fault tolerance;
5. Modular architecture. Filters include gzipping, byte ranges, chunked responses, XSLT, and SSI. Multiple SSI inclusions within a single page can be processed in parallel if they are handled by FastCGI or proxied servers.
6. SSL and TLS SNI support.

1. Mail proxy server features:
2. User redirection to IMAP/POP3 backend using an external HTTP authentication server;
3. User authentication using an external HTTP authentication server and connection redirection to internal SMTP backend;

Authentication methods:
1. POP3: USER/PASS, APOP, AUTH LOGIN/PLAIN/CRAM-MD5;
2. IMAP: LOGIN, AUTH LOGIN/PLAIN/CRAM-MD5;
3. SMTP: AUTH LOGIN/PLAIN/CRAM-MD5;
4. SSL support;
5. STARTTLS and STLS support.

Other HTTP features:
1. name- and IP-based virtual servers;
2. keep-alive and pipelined connections support;
3. flexible configuration;
4. reconfiguration and online upgrade without interruption of the client processing;
5. access log formats, bufferred log writing, and quick log rotation;
6. 4xx-5xx error codes redirection;
7. rewrite module;
8. access control based on client IP address and HTTP Basic authentication;
9. PUT, DELETE, MKCOL, COPY and MOVE methods;
10. FLV streaming;
11. speed limitation;
12. limitation of simultaneous connections or requests from one address.

The license of this software is Freeware, you can free download and free use this web server software.