MailBakup - Mailbakup is an all-in-one IT solution that provides an in-demand set of e-mail backup solution to save valuable data from the web-based email account to location derive easily and quickly.
Roundcube - Web-based IMAP email client
Vaultastic - Vaultastic’s on-demand SaaS platform provides Protection, Visibility & Control for your Critical Business Data with Agile Cloud Archival.
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.
MailArchiva - MailArchiva is an email archiving, email compliance, and e-Discovery enterprise server.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.