The Calendar Checking Tool for Outlook is a command-line program that checks Outlook Calendars for problems. To use this tool, the Outlook calendar must reside on a Microsoft Exchange Server. The tool does not work with IMAP, with POP3, or with other non-Exchange mail servers.
The tool opens an Outlook profile, opens the Outlook Calendar, and then checks several things such as permissions, free/busy publishing, and auto booking. Then, the tool checks each item in the calendar folder for problems that can cause items to seem to be missing or that might otherwise cause problems in the Calendar.
Although this isn’t an official Microsoft application, it is however developed by Randy Topken who is an Escalation Engineer at Microsoft and has been supporting Exchange since its first release in 1996 (in other words: this is a very reliable application). The application is hosted on Microsoft’s software development website GitHub and documentation is available on Microsoft’s official support pages.