vmail-sql is a complete virtual domains email setup, including sample Exim configuration sections, reference to tpop3d which will authenticate access to mailspools against the virtual user database, a set of admin-level scripts for administrating domains, and a Web-based control panel. Rather than storing the virtual domains setup in flat text files, it uses a MySQL database, allowing flexible administration strategies without concurrency hassles. It is designed for use in environments where several virtual domains are operated from a single machine/IP address.
vpopmail (vchkpw) is a collection of programs and a library to automate the creation and maintenance of virtual domain email configurations for qmail installations using either a single UID/GID or any valid UID/GID in /etc/passwd with a home directory. Features are provided in the library for other applications which need to maintain virtual domain email accounts. It supports named or IP-based domains. It works with vqadmin, qmailadmin, vqregister, sqwebmail, and courier-imap. It supports MySQL, Sybase, Oracle, LDAP, and file-based (DJB constant database) authentication. It supports SMTP authentication combined with the qmail-smtp-auth patch. It supports user quotas and roaming users (SMTP relay after POP authentication).
xmailheaders is a mail notification utility that is based on the "mailbox" utility that's avilable on Solaris workstations. The idea is that it sits on your desktop somewhere, periodically polling the mail server/spool for new messages. New message headers are displayed as they come in. Supported mailbox formats are POP3, IMAPv4, and Unix mbox. SSL-based password authentication is also supported for POP and IMAP.