Many times when I'm using Zimbra, I notice that the new message count in my inbox folder is greater than the number of new messages shown in the message list. If I then click on the "Get Mail" button, it manually updates the message list and the new messages appear.
Why does this happen? If Zimbra is able to update the message count automatically, why can't it also update the actual messages in the list? The user shouldn't have to constantly click on "Get Mail" in order to force the message list to update.