Mailtraq

Mailtraq provides full scale
mail routing and management, mailing lists, automated dialup handling,
user accounting, content barring, anti-relaying, anti-spam and
anti-virus facilities.
Mailtraq is extensible through a scripting
language and can collect and route mail from a single POP3 mailbox for
multiple users. Mailtraq also supports ETRN and ODMR for mail
collection. The Mailing List CRM feature can share incoming mail
amongst multiple users (for example, sales@yourcompany.com) and you can
host large discussion forums using e-mail based subscription handling.
Local Directory services (provided through LDAP) allow local users to
look up e-mail addresses hosted in Mailtraq.