How long does it take to upgrade a Zimbra server?

This is highly dependent on the number of mailboxes and Zimbra servers in your organisation as well as any customisation that may have been performed. For a single Zimbra server in an organisation for 25 to 900 mailboxes the upgrade process takes 30 to 45 minutes.

How often are Zimbra upgrades released?

Zimbra upgrades are released every 2 to 3 months and include bug fixes as well as new features. Patches are released for critical security issues, as required. The release schedule for Zimbra is available in the Zimbra Product Management Portal and provides details of all bugs, features and the corresponding release schedule.

What is the process of applying a Zimbra upgrade?

Schedule downtime for the Zimbra server. Perform a complete backup of the Zimbra server data. Download the latest Zimbra upgrade. Install the upgrade over the existing installation. Check results. The actual Zimbra upgrade process itself can take 30 to 45 minutes or more depending on the size of the installation, number of servers, complexity etc.