Outlook 2016 for Mac repeatedly prompts for authentication

To work around this issue, delete any cached passwords for your account and any modern authentication tokens from the Keychain. To do this, follow these steps.

  1. Exit Outlook and all other Office applications.
  2. Open Keychain Access by using one of the following methods:
    • With Finder as the selected application, click Utilities on the Go menu. Double-click Keychain Access.
    • In Spotlight Search, type Keychain Access and then double-click Keychain Access in the search results.
  3. In in the search field in Keychain Access, enter Exchange.
  4. In the search results, select each item to view the Account that’s listed at the top, and then press the Delete key. Repeat this step to delete all the items for your Exchange account.
  5. In the search field, enter adal.
  6. Select all items whose type is MicrosoftOffice15_2_Data:ADAL:<GUID>, and then press the Delete key.
  7. In the search field, enter office.
  8. Select the items that are named Microsoft Office Identities Cache 2 and Microsoft Office Identities Settings 2, and then press the Delete key.
  9. Quit Keychain Access.