Recently had a user who’s accepted meeting requests were going straight to their Deleted items instead of being displayed in their Inbox

• Checked in Mail and Calendars settings in Outlook which all were the default
• Checked Delegate Permissions for the user
• Check the Rules inside of Outlook Nothing there

Closing all Outlook windows and trying this again , the accepted meeting request still went the deleted items in Webmail which showed this was server side not Outlook/Client Side.  

Turns out there was a specific Webmail Server side Inbox rule/filter doing this which was not displayed in the Outlook Client. Disabling this resolved the issue