When you view a summary of your messages in a particular folder, you can sort by Address, Subject, Date, or Size. You can sort in ascending or descending order. For more information, click here.
From the Options and Styles... menu, select Preferences under My Options.
On the User Preferences page, locate Initial sort criteria and select Address, Subject, Date, orSize.
Click the Save button at the bottom of the table you are working in when finished.
Note: Sorting can also be done directly on the mail list by clicking the header you want to sort by. Clicking a second time changes the sort from Ascending to Descending.