Kasper, Did you change your AD FS to send email address attribute in the SAML assertion? Would you be able to send me the SAML response that is being sent by your AD FS to ArcGIS Online after authenticating the user? The ArcGIS forums have a messaging system built in, can you send a private message with the SAML response? I can take a look at the SAML response and see if we are getting the email address or not. You can use any of the network monitoring tools such as SAML tracer, fiddler, etc to capture the SAML assertions being sent in the HTTP requests. -Lalitha, ESRI.
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