Microsoft has opened up a public preview for Outlook.com Premium. The service will cost $19.95 for the first year, and it will offer an ad-free experience along with custom domains.
The service is open to anyone in the US that's already been migrated to the new Outlook.com. If you've been anxiously awaiting the new experience and thought that you could pay Microsoft to get it done through Outlook.com Premium, you're out of luck; we checked. It delivers a message that states that you won't be able to upgrade for a few weeks, suggesting that you create a new Microsoft account instead.
As noted above, the price for the first year is $19.95; after that, it jumps to $49.99 per-year. In a FAQ, Microsoft notes that the custom domain will be free during the first year, but will be renewed at "then current prices":
For Outlook.com Premium subscribers, a personalized email address is included for free for the first year with your Outlook.com Premium subscription. Your subscriptions to Outlook.com Premium will auto-renew annually at the then current prices. There will be an additional charge per year for your custom domain, if you select a new domain during the registration process. To cancel and to check current subscription prices see https://premium.outlook.com. Custom Domain subscriptions are not available on a stand-alone basis; a concurrent Outlook.com Premium subscription is required.
It's also worth noting that you won't own the domain. Microsoft buys "the domain on your behalf", and retains ownership of it.
You can sign up for the Outlook.com Premium preview right here, where you can also find out more information about the service.