I'm trying to use Outlook.com for my custom domain email accounts.  When I go to the Custom Domains Admin Center at domains.live.com I enter my domain and click Getting Started I am asked to provide my domain name.  When I do I get the message "This domain name can't be used with Admin Center because it's already registered with Microsoft. If you own this domain and want assistance please contact support."  So that's what I'm doing.

I know I registered this domain with Microsoft when I signed up for the Office 365 Preview, which has now expired.  I have been and am still receiving email on the primary email address that I used when signing up for Office 365, but the secondary email addresses I added to the Office 365 Preview have stopped working.  This makes sense: I need to set up those additional accounts outside of Office 365.  the question is, WHERE DO I GO TO MANAGE A DOMAIN THAT IS "ALREADY REGISTERED WITH MICROSOFT"?  There doesn't seem to be a link to any domain admin page.