If you’re running out of storage space on your hosted exchange e-mail account, you might be tempted to create Outlook Personal Folders. Be very careful with this approach. It will help you avoid data storage overage limitations in the short term, but you may be lulled into the false sense of security that your data is as safe as the rest of your e-mail and contact data; i.e., that is synchronized with the Exchange Server.
Outlook Personal Folders are stored on your local hard drive. You can see this when you actually create the Outlook Personal Folder, officially known as an Outlook Data File. The creation process directs you to the default location of any other outlook data files on your local hard drive, e.g., My Documents\Outlook Files.
The simpler and more secure way to create more storage capacity on your Outlook folders is to sign up for a service that provides more data storage than you may ever need. For example, an Office 365 Exchange Online account provides 25 GB of storage per user. I have over 16,000 unread e-mails in my Inbox, and I still have only used 1.75 GB. What would it take to reach 25 GB? (I personally don’t bother deleting e-mails for the most part, and I rely on the powerful search function to find whatever e-mail I need, so I don’t bother with subfolders either.)
And I think before I ever get close to the 25 GB limit with Office 365, my emails will be archived. We archive all our e-mail over one year old — just to keep the mailboxes to a manageable size, and not slow down the PC / laptop performance. These archives are also synch’d to the Exchange Server — so, all-in-all — no worries. And that’s the way it’s supposed to be!