Apache James

James stands for Java Apache Mail Enterprise Server. This software has a modular architecture based on a rich set of modern and efficient components that provides at the end complete, stable, secure and extendable Mail Servers running on the JVM.
James manages the Apache Mailet API which defines “matchers” and “mailets”. These allows users to write their own mail-handling code, build a message archive, or filter spam. A matcher is used to classify messages based on some criteria, and then determines the appropriate mailet for processing.