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Outlook is not authenticating successfully via Desktop Single Sign On
Published: May 8, 2017   -   Updated: Jun 22, 2018

Issue: Attempting to log into Outlook via Desktop SSO (IWA) results in an error or simply times out.

Applies To: 
  • Outlook
  • Desktop SSO
  • Office365
  • Modern Authentication (ADAL)

Cause: Modern Authentication now requires Outlook to authenticate via HTTPS

Resolution: Reconfigure IWA to use SSL
  • Refer to the Configuring SSL section of our Install and Configure the Okta IWA Web App for Desktop SSO Guide to enable HTTPS on IWA
    • We strongly recommend utilizing a public SSL certificate by a Certificate Authority such as GoDaddy (or a Certification Authority server on your domain), to eliminate the need to manually trust the certificate on each client
  • to trust the certificate on systems running OSX:
    1. If using a self-signed certificate, launch Safari and navigate to your Okta tenant
    2. Click "Show Certificate" in the "Safari can't verify the identity..." window that appears:
    3. Expand "Trust" and select "Always Trust" from the "When using this certificate" drop-down box:
User-added image
  1. Enter your user credentials when prompted
  2. Launch Outlook and sign on as normal.

Related article: Cannot sign into an Office 2016 application on Windows 10