Gmail is headed for the office — officially.

Starting Monday, Google will offer Google Apps for Your Domain, a free package of programs for businesses, universities and other organizations.

Workers will be able to send e-mail with Gmail, Google''s two-year-old Web-based mail service, but messages will carry their company''s domain name. The package also includes Google''s online calendar, instant-messaging service, and Page Creator, a Web page builder.

Information technology administrators can make some customizations. "But really, the applications are exactly what you''d experience as a consumer if you use them," said Dave Girouard, VP and general manager of Google Enterprise, a division of Google Inc.

The free edition of Apps for Your Domain is, like Google''s main site, supported with ads. By the end of the year, the company also plans to launch a paid version that will offer more storage, some degree of support, and likely, no ads. A price for this edition hasn''t been set.

Providing e-mail and other applications for businesses moves Google closer into what has traditionally been turf occupied by Microsoft Corp. Earlier this year, Google released a program that builds simple Excel-type spreadsheets but lets users access them on the Web.

Now, with e-mail, Google appears to be targeting Microsoft''s Outlook and Exchange franchises — although the company plays down any such views.

"We don''t see our products as an either/or thing right now," Girouard said. "Smaller businesses, it may be the case where this is the preferred e-mail and messaging solution. In larger companies, it may well be used alongside."

In February, Google launched a beta test with San Jose City College in California; by the end of the beta, the company said hundreds of universities had signed up, along with one-person businesses, medical and legal practices, even some companies with tens and hundreds of employees.

For all of Google''s side projects — spreadsheets, shopping, maps — its revenue is almost entirely based on its search advertising.

While Girouard said the market for enterprise e-mail and other products is very large, he declined to speculate on the financial implications. "We tend to focus first on user adoption," he said. "The business model follows pretty successfully."

For businesses, Google hopes the suite of applications will relieve some of the cost and annoyance of administering e-mail servers and the like — and hopefully, fewer calls to internal help centers.

After AOL''s recent data privacy debacle, businesses may have qualms turning their employees'' data over to Google.

"Third-party hosting providers aren''t necessarily any more risky than their own companies," said Girouard. "Google has hosted applications and information for individuals, and is starting to do it for organizations. We do have a very good track record," he said.