Outlook 2010 shows desktop alerts for new mails and these alerts are combination of sound and notifications. Sometimes when working on something important, these notifications could be annoying and disturbing to work. You can change the notifications for Outlook new email to suit your work. You can also disable these alerts or set how long these alerts should display in case you have enabled them.
To change alerts, click the file menu and select Options.
In the options, select Mail on the left hand side and scroll down to Message arrival section.
Here you can enable or disable message alert settings including sound, mouse pointer, show an envelop and also display a desktop alert. You can also configure the desktop alert settings by clicking the button next to it.
You can make the desktop alert shot or long based on your needs. Once set, you can also preview them before activating it. Click OK and close the option window.