Does the Zimbra server have to be taken offline to do backups? Is there any way to do a live backup?

Zimbra backups are performed LIVE, the server remains operational and accessible, this is a unique feature of Zimbra Network Edition. Zimbra Open Source Edition does not have the same backup/restore feature. The Zimbra full backup process places the account’s mailbox in maintenance mode to temporarily block mail delivery and user access to that mailbox. and Returns that account’s mailbox to active mode and moves on to the next one. For more details see the Zimbra Administration Guide.

How does the Zimbra backup feature work?

Zimbra performs a “hot” backup (no downtime). By default, two full backups are performed each week. With daily incremental backup (about 10% size). Backups are retained for 2 weeks. As a guide, reserve x2.5 total mailstore size for backup storage (plan for growth!). Both users and administrators can restore mailboxes from backups easily. It is a simple point’n click action. Backups can be restored to point in time, to a new mailbox or restore to the active mailbox.