vpopmail provides support for hosting virtual email domains on mail servers running qmail.
It easily supports from 1 to over 100,000 domains. It also supports from 1 to millions of email accounts per domain. It automates and simplifies many of the tasks needed to manage virtual domains . User authentication information can be stored in hash files, mysql, oracle, sybase, postgreSQL or LDAP. The programming API simplifies writing addon software, such as qmailadmin, vqregister and many other vpopmail compatible programs.
vpopmail has an active development and support community and is running world wide in at least 80 different countries.