"An unknown error has occurred" error message in Outlook

• Related Articles

• Office 365 Online Archiving is not show in Outlook 2016

  The “In-place Archive” feature is only available with Office Professional Plus licenses or when you are using a standalone installation of Outlook.  For Office 365 Business Premium and Business, the “In-place Archive” feature is not available in ...

• Outlook 2016 failed to attach file stored in OneDrive as a copy

  Solution: https://www.msoutlook.info/question/attach-instead-of-link-to-onedrive-files

• Email sent from shared mailbox not saved to Shared mailbox's sent item (outlook 2010)

  https://support.microsoft.com/en-us/kb/2181579