GroupServer is a Web-based mailing list manager designed for large sites. It provides email interaction like a traditional mailing list manager but also supports reading, searching, and posting of messages and files via the Web. Users have forum-style profiles, and can manage their email addresses and other settings using the same Web interface. It has supports features such as Atom feeds, a basic CMS, statistics, multiple verified addresses per user, and bounce detection, and is able to be heavily customized.
PigeonReader is the Web mail client of the PigeonAir project, a solution for easily building clustered, scalable, and modular email services. PigeonReader is completely UTF-8 compliant, allowing any charset to be used. It is based on XML, which allows skins and themes to be easily written using the XSLT language. It was written to be easily used in a cluster of Web servers, where multiple and different domains are to be managed transparently to the end user, possibly with different skins, features, and configurations.