The Microsoft Online Services Team Blog features a post on Domain validation. Since we get a lot of questions about this topic it seems useful to share :
Domain Validation and BPOS
Tips and Tricks
By Brett Hill of Advaiya, Inc. for Microsoft Corp.
When you sign up for an email service like Exchange Online, you’re probably planning on using your own domain name for signing in and for your email addresses. I can actually validate a domain in about 2 minutes or less, but there are a couple of things to know.
When you first signup for BPOS, you’re asked to provide a domain name. This is used to create a base domain like “myverycooldomainname.microsoftonline.com”. You’re issued a microsoftonline.com domain (sometimes called the Microsoft Online Default Routing Domain [or MSODRD for the real trivia geeks out there]) as it is certain to be unique to the Microsoft Online AD and you don’t have to immediately prove ownership. In this way Microsoft can immediately configure your BPOS account. …
Continue at source : Domain Validation Tips and Tricks