London, Feb. 27: Microsoft was this morning struggling to find out why tens of millions of Hotmail users were left without access to their email accounts yesterday.

Access to all of Microsoft’s Web-based communication tools — including Hotmail and instant messaging accounts — was blocked across the globe for several hours in the early afternoon yesterday. The problems, which affected the 80 million people who use Hotmail worldwide, were fixed within a couple of hours, Microsoft said. This morning it said that Hotmail users were able to log in again, although the company would not elaborate on the cause of the outage.