Interesting. I didn't realise Apple supported multiple domains. That must have happened after I moved away. I actually went the other way from Apple to Microsoft. I run a Linux laptop and iPhone, and the kids run all Apple kit. I've found the Linux support for MS better than for Apple (Evolution for email and calendar; OneDrive for live home directory sync across devices; and I use Firefox for password synchronisation). I tried to find a way to use iCloud storage for file sync with Linux but found nothing.