Google has opened its Gmail email service to all comers, dropping the beta service's invite-only status.

Google launched Gmail in April 2004, and the company has been steadily integrating new features. The service remains a beta release. It includes Google Talk, an instant messaging program, and a calendar, plus other features such as spam filtering.

Gmail users previously had to pass along invitations to others so they could register for the service.

The company has positioned Gmail as a gateway to other online offerings by displaying links to its Picasa photo sharing service and Docs and Spreadsheets, a word processing and spreadsheet application.

Google has concentrated on building its infrastructure for its service-based offerings. As of Wednesday, Gmail offered users about 2.8GB of storage space for email, one of the most generous limits for free services.