The software consists of both client and server components. Two versions of Zimbra are available: an open-source version, and a commercially supported version ("Network Edition") with closed-source components such as a proprietary MAPI connector to Outlook for calendar and contact synchronisation.
Zimbra Desktop is a full-featured free desktop email client which is still supported in version 7 but has reached End of Life in version 7.2.2 and will be replaced with an HTML5 offline mode in version 9.
The ZCS Web Client is a full-featured collaboration suite that supports email, group calendars and document sharing using an Ajax web interface that enables tool tips, drag-and-drop items, and right-click menus in the UI. Also included are advanced searching capabilities and date relations, online document authoring, "Zimlet" mashups and a full administration UI. It is written using the Zimbra Ajax Toolkit.
The ZCS Server uses several open source projects (see the section, Included open source projects). It exposes a SOAP application programming interface to all its functionality and is also an IMAP and POP3 server. The server runs on many distributions of Linux as well as on Mac OS X
ZCS can synchronize mail, contacts, and calendar items with open-source mail clients such as Evolution and also with proprietary clients such as Microsoft Outlook and Apple Mail, but only through proprietary connectors available exclusively in the commercially supported version. Zimbra also provides native two-way sync to many mobile devices (Nokia Eseries, BlackBerry, Windows Mobile, iPhone, Android).