Calendar Repair Assistant - Delete re-created calendar items - Exchange 2013/2016

Behind the scenes, the Exchange E-Mail Server runs a tool called Calendar Repair Assistant (CRA), which "detects and corrects inconsistencies" in meeting information. It makes sure that the meeting time, location, and attendee information on the calendar of the person who proposed the meeting matches the information on everyone else's calendar (and vice versa).

Users may not notice the Calendar Repair Assistant (CRA) at all, or may see one of the following:

• A meeting you deleted from your calendar reappears.
• You see the message "Your meeting was found to be out of date and has been automatically updated."
• You see this text appended to the bottom of the meeting notes:

Exchange re-created a meeting that was missing from your calendar. The meeting was re-created because the meeting organizer previously received an Accepted or Tentative response from you. To make sure the calendar item is up to date and the organizer has your latest status, please accept or decline the meeting from within your calendar.

It may look like this (Screenshot of Outlook 2016 with Exchange 2016):

The most common reason the Calendar Repair Assistant needs to "fix" your calendar is that you deleted a meeting from your calendar (or deleted the meeting invitation) rather than Accepting or Declining it. You should always choose Accept or Decline, either in the invitation or on your calendar. If, later, you decide you cannot attend a meeting you accepted, highlight the meeting on your calendar, then click Decline in the toolbar or ribbon. Don't just delete the meeting.

• To delete returning calendar items please use Outlook Webmail and delete the entry.

Another cause of calendar discord can occur when you use a mobile device to accept or decline a meeting. We strongly recommend that, when it comes to your calendar, you only use your mobile device for viewing, not accepting or declining. Use Outlook or Outlook on the Web to accept or decline meetings.

Source: https://it.cornell.edu/facstaff-email/calendar-repair-assistant