Camunda - The Universal Process Orchestrator
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Appian - See how Appian, leading provider of modern low-code and BPM software solutions, has helped transform the businesses of over 3.5 million users worldwide.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Kintone - Build business apps and supercharge your company's productivity with kintone's all-in-one...
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.