Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Zetadocs Delivery - Automated document emailing
Kolab Community - Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.
Zoho Docs - Zoho Docs is an online document management software that lets you manage and store all your files on the cloud. Share, collaborate and access all your files on multiple devices.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Zetadocs Capture - Invoice processing, accelerated