A rather handy feature available in Outlook is the New Mail Desktop Alert. When enabled and you receive a new message, a semi-transparent notification appears in the bottom right corner of your desktop which shows you the sender and subject of the new message. Additionally, you can click on the notification to open the full message.

I have found this option most handy when I am working on something which requires full use of both of my monitors. This way when I get a new email message, I don’t have to restore Outlook to see if it is something I need to address. If it is important, I click on the notification and respond, however if it can wait, I just let the notification go away on its own and continue working.

You can enable or disable this function by right clicking on the Outlook icon in your system tray and selecting the “Show New Mail Desktop Alert” option. This option is available in Outlook 2003/2007, but I am not sure about previous versions.