PURPOSE How to recognize and respond to mailbox storage quota problems. GENERAL STEPS Open Outlook, Outlook on the web, or the approved mail client and confirm you are signed in with the correct work account. VERIFY RESULTS Check whether mail, folders, calendars, shared mailboxes, or delegate access behave as expected after the change or troubleshooting step. TROUBLESHOOTING If the problem continues, note the mailbox involved, approximate time, error message, affected folders, whether webmail works, and whether other users are affected. BEST PRACTICE Use Outlook on the web as a comparison test when desktop Outlook behaves strangely. If webmail works but desktop Outlook does not, the issue may be local to the client.