Microsoft's paid take on email, Outlook.com Premium, is officially open for business: the company has quietly dropped the Preview label on its service, making it available to anyone in the US. Spend $50 per year ($20 if you act before March 31st) and you'll get an ad-free inbox, custom domain support for up to five users, info sharing between those people. You won't get the custom domain itself with your subscription, but Microsoft can do that for $10 per year if necessary.