Windows Live Custom Domains allows you to utilize WL Mail for your domain. There are a few things I'd like to see, tho. First, I'd like to customize the URL I use to access the site. Instead of mail.live.com, I'd like mail.michaelflanakin.com, for instance. Next, it'd be nice if I could sign in without specifying the domain name. Not a big deal, but it'd be nice. Lastly, I wish I could customize the look and feel of the site used to access email. Since WL Mail is built with .NET, a master page seems the best solution here. I'm sure there are certain requirements of the UI, but I'd be willing to work around those to get the look and feel I want.
Edit: I just reported this, but seeing as tho WL feedback isn't published, I doubt we'll hear back about this anytime soon. I need to see if there's an internal resource to discuss feature requests.