Personal folders are useful for storing mail on your hard drive within Outlook. These directions show you how to create Personal folders. (If you are using the Google@Wharton service, see: Backing Up Google@Wharton Account Data (Google Takeout Service) for directions on making a backup without using Outlook.)
Please note: These instructions will only work if you have Outlook configured to access your Wharton email. This will not work if you are using Webmail, and any messages or other information you place in a personal folder won't be available to you when you use Webmail.
Microsoft's Support site has excellent directions on managing personal folders. Choose the version of Outlook you're using, and the level of support you want:
Outlook 2013, Outlook 365
Exporting Mail to .pst: http://office.microsoft.com/en-us/training/need-a-copy-use-export-RZ010238639.aspx?section=6