Working Offline in Zimbra 8.6

Working Offline

When you are working offline, only the items that are in the ZDB that are on
your computer are available. If you configured the settings to download
headers only, only the messages that you have downloaded are available.
New mail is not synchronized to your computer until you go online and
connect to the Zimbra server. Email that you create while working offline is
saved to your Outbox and is automatically sent when you connect to the
Zimbra server.