Sak? Mail is a very high-performance carrier-class Web-based email system, designed for scaling to large numbers of concurrent users. It takes advantage of the Java Servlet APIs memory-resident architecture and multi-threading HTTP response model. It avoids file system accesses through memory caching at every possible point, and never needs to touch the file system at runtime at all if coupled with an IMAP server. It supports POP3, IMAP, and SMTP, including authenticated SMTP. It also provides an extremely sophisticated message rendering system that can easily handle even complex HTML encoded messages with attachments that have been forwarded multiple times.