If you are receiving errors about being close to your quota for your Exchange e-mail account, follow the instructions given to attempt to decrease the amount of e-mail saved to your online account in an attempt to avoid reaching your quota.
Open Outlook. Open your Exchange Inbox.
Items in the Inbox will now be grouped in close proximity to size. Items in the Enormous, Huge, and even Very Large are ones you might want to delete or simply remove the attachments from.