Outlook has an option to change the importance level for email message from Normal to Low Importance or High Importance. This can be done using the option available as New Message window.
The default message importance level in Outlook 2013, 2010 and 2007 is set to Normal. But when you going to frequently send emails with High importance then it is recommended to change the default importance level to High. Listed below are steps to change the default importance level for email messages In Outlook 2013, Outlook 2010 and Outlook 2007
Step 1: Launch Outlook 2013 and click the File menu.
Step 2: In the Outlook Options window, click the Mail Settings.
Step 3: Scroll down to the Send messages section in Mail Options and click the drop down with the caption as Default Importance Level.
Pick your desired importance level from the drop down values and click Ok to confirm and save the changes.
Now any messages that is being sent from Outlook will have the newly set value for importance level .