HamCannon is a Zope/Plone product for managing outbound email marketing. HamCannon is designed for sending ham, not spam: it has much support for helping users unsubscribe and none for hiding from them. HamCannon provides all of the tools required to produce personalized email newsletters or other email marketing, with subscription management, open tracking, bounce tracking and link tracking, complete statistical reporting and complete personalization, limited only by your data.
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.