command line tool to manage email (alias-)domains/accounts/aliases …
vmm is the easy to use and configurable command line tool for administrators and postmasters, to manage domains, alias-domains, accounts and relocated mail users. It allows the fast and easy management of mail servers.
vmm is written in Python. It's designed for installations using Dovecot and Postfix with a PostgreSQL backend.
DataSync Suite is an open source platform for integrating tools like Zimbra, SugarCRM, and Drupal. The tool is focused on a single sign-on, application data integration, and fast, flexible deployment.
Virtual Qmail - virtual domains management system for qmail. It is designed to be fast, reliable, and easy to use. Includes software allowing users to manage their accounts via WWW.
Ni!Mail is a webmail connecting to an IMAP server and using python/nevow/twisted to provide a clean and fast interface. It uses nevow livepage, a library that uses XMLHTTPRequest, to make it very dynamic.