Gossamer Mail

A feature-rich web-based email system that offers your visitors accounts accessible via their browers or with the addition of a plugin, through their desktop clients as well. It includes all the features you'd expect to find in a quality email system like user customizable folders, full MIME support for sending/receiving of attachments, global and user-based email filters, address book and nickname support, supports sending/viewing of html mail, advertisements can be added to all outgoing mail easily and much more.