According to TechCrunch, Facebook will unveil Project Titan at a press event in San Francisco on Monday. A source had previously told the site that Facebook was planning a 'fully-featured webmail product' aimed at Google's own email offering.
Facebook's existing messaging service has been criticised for being slow and intrusive. The Facebook e-mail service - we'll call it Fmail, or Fail for short - would be aimed at the site's 500 million users.
It is likely to offer heavy integration with the social networking platform, serving up news feeds, photos, status updates and an instant messenger client.
Facebook has a habit of launching new features slowly to only a few select users to test for bugs, so it remains to be seen whether the new service be widely available at first.