Outlook Premium, the previously-revealed subscription service that will add new features to Microsoft's Outlook.com web email site, is entering a new testing phase. A new report says that the company is testing a standalone version of the service that will cost $3.99 a month.

Outlook Premium

Thurrott.com reports that Microsoft is sending invites to an unknown number of customers to try out the service. The offer gives them one year of Outlook Premium for free, after which the regular $3.99 a month charge will kick in. Previous reports claimed that Microsoft may also give access to Outlook Premium for free for free to Office 365 subscribers.

Outlook Premium will offer users up to five personalized email address and will be ad-free, along with offering better ways to share calendars, contacts and documents. Microsoft has not yet officially announced the service and it's possible that features and pricing for Outlook Premium will change before it comes out of its testing period.