Open-Xchange is a groupware solution that provides an alternative to Microsoft Exchange. The diversity of functions ranges from email, appointment, contact, and task management, through to documentation exchange and project management. Open-Xchange is flexibly extensible via its plugin system. Open-Xchange is often used together with the Postfix mail transfer agent and the POP and IMAP server Cyrus. The software provides a web-based interface whose development follows the Ajax concept. There is also the option of using various mail user agents, such as Microsoft Outlook, Mozilla Thunderbird, or Apple iSync, to access the Open-Xchange server.