When Entourage is configured as an IMAP client it creates a local cache of messages to speed up message opening. Remember that IMAP keeps all the emails on the server. The messages you're looking at are just a local copy, a cache. This cache sometimes gets corrupted and needs to be flushed and recreated. The most common signs of corrupted cache are: you can't delete messages, or they get deleted and then come back, you can't move messages between folders, you don't see new emails even though Entourage appears to be downloading new emails, the list of emails is incomplete or garbled or you see multiple copies of messages.
Step by step instructions
First, click once on the server name in the left pane, not the Inbox, to select it.
Then right-click or (Control-click) on it to invoke a contextual menu and chose Empty Cache...
You will see the following warning, make sure you understand the implications - all flags and links will be removed, this may seem radical, but is largely unavoidable. This includes the flags as well as the reply indicators. It will empty cache for all mailboxes, not just the Inbox!
This is the Emptying cache progress window, it may take several minutes if you have thousands of messages in you mailboxes...
When you go to your Inbox, or any other mailbox now, it'll appear to be empty. Don't panic, remember that these messages are just a mirror and the originals are kept on the server. After emptying the cache Entourage needs some time to re-download the email messages.
if this doesn't happen for a few minutes then right-click (or Control-Click) on the Inbox (or other mailbox) and select Refresh Message List. This should do the trick.
Re-downloading of messages will take even longer than emptying the cache. Observe the Progress window and wait patiently, don't interrupt, this process must be competed or you may end up with corrupted cache again.
if you don't have your Progress window open go to Window menu and select Progress or type Command-7 (Apple-7) on your keyboard.
