Microsoft has fixed a bug that prevented some users from receiving emails on Outlook.com, ,but mobile users might still be having problems.
The software giant has also resolved issues related to SkyDrive users, who reported problems while retrieving their files.
Blaming the breakdown on an unexplained incident, Microsoft claims only a small number of users had been affected.
In May 2013, Microsoft moved all its email users including those with the hotmail and msn accounts to Outlook.com, adding two new features for users, including SMTP and deeper integration with SkyDrive.
Launched in February 2013, Outlook.com is claimed to have about 400 million active accounts, which include 125 million using email, calendar and contacts via Exchange ActiveSync.
