Outlook Indexing Issue (cached mode) and slow start up.
Some users have reported excessive wait times when opening Outlook and some issues have also been reported where emails are not indexed for searching purposes.
Please ensure that when you shut down/restart your computer that you close Outlook first and wait for it to close completely from your tray (bottom right, shown in the image below). Then start the shutdown process as normal.
If Outlook is not closed completely or crashes unexpectedly it can cause your PST (non-exchange) or OST (exchange) files to become corrupt or contain errors.
When you select the shutdown process, applications that do not respond quickly enough for Windows to close down on its own will be terminated forcefully instead, this is by design but can cause issues with Outlook!