Outlook 2016 for macOS, Authentication Failure, O365

Outlook 2016 for macOS, Authentication Failure, O365

Date published
December 29, 2016
Tags
macOS

Intended Audience

People experiencing Authentication Failure with Outlook 2016 for macOS and O365.

Symptoms

  • Outlook 2016 for macOS stopped being able to connect to O365 and check mail, no error displayed at this stage.
  • Credentials are definitely correct, still able to access O365 mail via iOS app and browser.
  • Deleting and re-adding the account within Outlook now throws up "Authentication Failure".
  • Uninstalling and re-downloading Office 2016 for macOS made no difference.

Resolution

Thank You Larry: Original solution article

Paraphrased:

Seems that the issue is caused by corruption of KeyChain entries related to Outlook.

  1. Go to KeyChain Access
  2. Search "Exchange" under Login --> All Items and delete everything
  3. Search "Office" and delete everything
  4. Search "ADAL" and delete everything
  5. Launch Outlook, try again