Apart from the customised domains, Outlook Premium would also offer an ad free experience, better calendar sharing. All of these you get for a $3.99 per month and it is yet not clear on if the Microsoft 365 subscribers will get it for no extra cost. The $3.99 we are talking about is for the standalone product. Things get hazier as Microsoft is still doing its pilot for the services, this means you need an invite to check out the Outlook Premium and believe me it is not easy to get one, even if you are already an Office 365 subscriber. On a related note Microsoft has partnered with GoDaddy for the domain and it is for free the first year post which the users need to pay the domain renewal fees every year. Pilot phase of any program is susceptible to changes, it would not be unreasonable to entertain the possibility of completely scrapping the project in case of negative feedback. The Price point might also change and if Microsoft plans on charging extra for Outlook Premium for the Office 365 users it could turn out to be a costly affair. Microsoft has been lately shifting towards the software as a service model, something that it also intends to do with the upcoming iterations of Windows. If you feel that the $3.99 is a bit more to spend on a premium email service, the Ad-Free Outlook priced at $19.95 per year might make more sense for you, though it omits some of the features that Premium offers. Microsoft is testing waters with the Outlook Premium and as ZDNet reported it all started back in 2014 when Microsoft started offering the custom domain services, a service they shut down eventually with the hopes of relaunching it as a standalone offering.