CIS Department Wiki
If you are unable to synchronize your mailbox, calendar, or contacts with data on the server this may indicate your Outlook cache needs to be re-created. You can verify that data on the server is correct either by using Outlook Web Access or a mobile device.
SPU Email accounts are connected to Office 365 through an Exchange connection. Instructions for troubleshooting this are located on Microsoft's Troubleshoot Cached Exchange Mode page.