pop3ml

This class can be used to manage or newsletters mailing lists using a POP3 account, whitout a local smtp server.

It works with php5 and mysql => 4. It's highly configurable by users.
You can subscribe/unsubscribe simply with mail messages. There is optional subscription/unsubscription confirmation,
subscription moderation, message moderation, digest message mode, parent/children list management, mail scheduling to
postpone a message, mail filter (procmail-like syntax), message queue for unsent emails, message size check,
command to retrieve messages, bounce detection, message header management, black/white list, multi rcpt-to smtp command
and others functions.