Thanks for following up on this - sorry, I took a few days away to get some writing done...

No change when adding an email account. One thing I noticed is that the URL it goes to in Iris for authentication is:

https://login.live.com/oauth20_authorize.srf

Whereas on Outlook on Windows/ Mac it goes to https://office365.outlook.com/ (or some similar URL to this from memory)...

The Microsoft login screen that says I don't exist looks identical to the one that does work on Mac/ Windows - so I'm guessing the method for authentication is similar between O365 and Live.com - but I can't seem to change the URL in the address bar, or see a setting to configure anywhere to go elsewhere for authentication...

Hope this makes sense? And thank you in advance for looking into it - I'm very grateful that there is such a committed community around this OS. I'm very much enjoying getting to grips with things :)