Was there ever any update on this @PaulMc ?   I think it’s to do with the Microsoft Intune SDK for iOS which they’ve wrapped all their Office apps in. I get a similar error trying to open links from Outlook in Edge on iOS.   Even though I’m using Meraki and don’t have InTune app protection policies enabled, I think it somehow defaults to not allowing cross-app communication...   I don’t think it’s related to Apple’s Managed Open In which containerises data because the popup  contains Microsoft account details rather than being a generic Apple one.   Let me know if you have any more information please ... View more

If this is for connection to your own Exchange server, then you'll need your own CA server, and to generate your own certificates for your users.   I haven't done it with Azure, but here are Azure instructions. https://docs.microsoft.com/en-us/azure/active-directory/authentication/active-directory-certificate-based-authentication-get-started ... View more

Where do I find / generate certificated in O365? Googling like crazy here, but can't find anything at all.. ... View more

  In your Profiles, one of the settings is "Managed App config". From there, select Outlook and put in the keys above.   A link to the Managed App Config guide is https://documentation.meraki.com/SM/Profiles_and_Settings/Using_the_Managed_App_Settings_Payload   ... View more