A Microsoft crash has locked thousands of email users have been locked out of their accounts today.
Website status monitoring service downdetector.com said there had been 1,276 reports of problems with Outlook today, which was previously known as Hotmail and is offered by Microsoft.
A spokesperson for the firm said: "We are aware of reports that some users are having difficulty signing in to some services. We are investigating this issue."
Skype users are also having trouble logging in to the chat service.
Some users said the service does not recognise their login details, with complaints coming from across the globe.
The issue is also affecting Xbox players, who can't access their Xbox Live accounts because they are run by Microsoft.
One user said on Twitter that Microsoft said it is working on resolving the issue, and hopes to have it fixed in "a few hours".
The @MicrosoftHelps Twitter account is currently being inundated with requests for help with logging in.