When you view a SharePoint Online list in Office 365 Enterprise, you receive the following error message:
The number of items in this list exceeds the list view threshold, which is 5000 items. Tasks that cause excessive server load (such as those involving all list items) are currently prohibited.
To work around this issue, review the recommendations, techniques, and tips outlined in the “Ways to manage lists and libraries with many items” section of the “Manage lists and libraries with many items” guidance located at the following Microsoft website:
This issue occurs because SharePoint Online uses the Large List Resource Throttling feature. By default, the list view threshold is configured at 5,000 items. When the defined item limit in a list is exceeded, the message is displayed.