"We have a lot of customers that moved to our Web client because they wanted to get off the Outlook upgrade treadmill," said Glenn Winokaur, Scalix's CEO.

Scalix counts more than 1 million e-mail boxes served by 10,000 e-mail servers among its 400 customers. Founded in 2002, Scalix licensed the former OpenMail software from Hewlett-Packard Co. in 2003, which was then at Version 7. New features in Version 11 include real-time indexing of public and private e-mails for fast searching, a delegation feature that gives administrative assistants access to calendars and e-mails of their bosses or created groups, and Web services interfaces that allow integration with ERP or CRM applications.

Scalix also allows customers to continue using their existing Outlook clients while simply swapping out their e-mail servers.

"This offers the advantage of a fairly seamless migration with no impact on how employees do their daily work," Osterman said.

Scalix's customers include Radisson SAS Hotels and Resorts, which serves about 1,000 e-mail users at 40 hotels in Europe; a Silicon Valley chip maker now in the pilot phase of a project to convert 7,000 Lotus Notes users to Scalix; and a San Francisco Bay area networking vendor that's moving 8,000 e-mail boxes to Scalix.