O365 iApp - Error: The Metadata Exchange URL in the domain registration isn't valid. URL:

Hi all,

We just setup SAML-Auth for o365 on F5 APM (11.6.0 HF6) using the official o365 iApp template. I checked with Remote Connectivity Analyzer (RCA) https://www.testconnectivity.microsoft.com an will get the following:

The Microsoft Connectivity Analyzer is analyzing the domain registration received for user userd@mydomain.com. 
  An error was found in the domain registration. 
 Additional Details  
The Metadata Exchange URL in the domain registration isn't valid. URL: 

Elapsed Time: 1 ms.

SAML Auth on F5 is working fine according to the APM logs. Unfortunately I could't find anything in the iApp setup guide regarding this "The Metadata Exchange URL". Does anybody has an idea where to define that on F5 SAML SSO Config? Or is it a Microsoft specific thing?

Thanks & Regards Thrillseeker