Microsoft has built in Skype to its Outlook.com webmail service.
The move allows users to make audio and video calls and send Skype instant messages via the website once they download a browser plug-in.
UK-based customers are the first to be offered a "preview" version of the technology. Germany and the US will follow "in the coming weeks".
However, analysts questioned whether the effort would help Microsoft regain ground lost to Google's Gmail.
