A tiny provider of open-source e-mail exchange software is using a disruptive pricing model to compete against Microsoft and other large providers of proprietary e-mail service technology.

As part of a deal announced Monday, Open-Xchange will provide its open-source technology to 1&1 Internet, an international Web-hosting company that plans to offer a hosted e-mail service for €4.99 ($6.00) per user per month or €2.99 per user with the purchase of 100 accounts or more, said Open-Xchange Chairman Rafael Laguna.

The service will launch this month in Germany and Austria, with France, the U.K., and the U.S. to follow in May.

Under a flat-rate pricing plan, 1&1 Internet will be able to offer a basic version of the Open-Xchange software to all its 2.7 million customers without having to pay any additional fees, according to Laguna.

In addition to open-source code and application programming interfaces, "disruptive pricing models like ours are another reason why companies choose open-source software," he said.

A premium version, which links with Microsoft's Outlook application and provides other features, will be available for a fee.

The 1&1 Internet e-mail offering, called MailXchange, will include calendar, contacts, and task management functions that are similar to those of Microsoft Outlook.

In addition to Open-Xchange, 1&1 Internet will continue to offer Microsoft Exchange and its own e-mail service software.

Open-Xchange, which is based in Tarrytown, New York, employs 54 people. It has product development and operational facilities in Nuremberg and Olpe, Germany.