In Microsoft’s infinite wisdom, they decided to not have an envelope icon show up in the systray (the icon area beside the clock) when new mail arrives for your IMAP accounts in Outlook 2010. I discovered shortly after installing Outlook 2010 and setting up my IMAP email account that I was not being notified of new emails.
To get desktop alerts and a sound, you can setup rules to do so when a new IMAP message comes in. However, for the envelope icon, you can try this nice little add-in from EmilStefanov.net.
“The Outlook Email Notifier is a plugin for Microsoft Outlook 2010 that displays an icon in the system tray when new email arrives. Outlook 2010 already has this feature, but it does not work for IMAP email accounts. This plugin works even with IMAP.” via Outlook Email Notifier – EmilStefanov.net.
Give it a try and see if it works for you. Maybe Microsoft will give us an update for Outlook 2010 that will do this very same thing.