This error affects Exchange server users with a large number of folders in their profile, either in their mailbox, public folders, or SharePoint lists. In most cases, you won't have a problem until you exceed approximately 1,000 folders, or a gigabyte of space is used.
Outlook works fine for a little bit (5-10 minutes) before users start getting this error:
Task 'Microsoft Exchange' reported error (0x8007000E) : 'Out of memory or system resources. Close some windows or programs and try again.' Cannot display the folder. There is not enough free memory to run this program. Quit one or more programs, and then try again. Cannot expand the folder. There is not enough free memory to run this program. Quit one or more programs, and then try again. Cannot expand the folder. There is not enough memory available to perform the operation.
When they close Outlook and reopen it, they can again work for a few minutes before the errors kick in. The error appears whenever clicking or expanding a folder (public folder or mailbox folder) except for the Inbox. When the error occurs, mail in the Outbox also doesn't get sent until Outlook is restarted.