AFAIK the remotewebaccess.com Microsoft personalized domain name feature of Anywhere Access is not currently working in Windows Server Essentials (and hasn’t been for many months now). Existing domain names may still be working (I don’t know for sure though), but setting up new ones is definitely not working ATM.

That being said… Once a personalized domain name has been assigned to your Microsoft (Live) account, I am not currently aware of any way to “release” it I’m afraid. I believe that they stay associated with the Microsoft account they were originally assigned to indefinitely, and each Microsoft account can have multiple personalized domain names associated with it. I thought that there was a limit of something like three to five personalized domain names allowed per Microsoft account, but I myself have accounts with more than that in them (and they don’t ever seem to expire seeing as I have some that are more than a decade old now even though I haven’t used them in many years).