I wish I had been paying more attention while I was doing it. I know that I did these three steps

1) Added my personal domain to the domain list. 2) Inputted my me@mydomain.com email address into some form. 3) Went to Outlook.com and saw someone else's name, and some else's contacts.

I'm pretty sure #2 is where the problem occurred. Hopefully someone at Microsoft familiar with the process will be able to figure this out. I'll provide the feedback.