If you are using Office 2016 for Mac and recently started seeing multiple authentication prompts, you may be using a new ADAL (Active Directory Authentication Library) and your Exchange Online tenant may not be enabled, thus causing authentication problems.1.
To resolve this issue for your Outlook for Mac clients (Windows Outlook can use ADAL, although it must be enabled, however Outlook was automatically updated and is looking for an ADAL Auth response from EXO), follow the steps below.
- Get the latest updates for Office 2016 for Mac:
- Use your Mac –> Office –> Check for Updates to make sure you are on the latest and greatest build, which is 15.21.1
- Enable ADAL for your Exchange Online Tenant
Turn on modern authentication for Exchange Online
- Connect to Exchange Online as shown here.
- Run the following command:
- Run the following command to verify that change was successful:
Get-OrganizationConfig | ft name, *OAuth*
- Restart your Outlook for Mac client and authenticate
Note – You should NOT receive multiple authentication prompts, although you may need to authenticate the first time, which is saved into your Mac Keychain!