Search engine Google is keeping the heat on its rivals with the upcoming launch of a free webmail service, known as Gmail.

The Mountain View, Calif.-based company said it is offering a preview version to a "small number of e-mail aficionados." When fully available, the free webmail service is expected to have the storage capacity of up to eight billion bits of information, the equivalent of 500,000 pages of e-mail. Per user.

When fully launched, Google said Gmail will include full e-mail search for every e-mail a subscriber ever sent or received using keywords or advanced search features. The offering also comes with 1,000 megabytes (1 gigabyte) of free storage -- more than 100 times what Yahoo! and Hotmail offer in their free versions. The webmail will also carry "highly targeted" advertisements similar to the ones found on a Google results page. A spokesperson for Google said it was too early for the company to consider a fee-based Gmail with extra storage or special features.

The company also said Gmail will eliminate the need to file messages into folders because each e-mail will be automatically organized into what the company calls "meaningful conversations" that show messages in the context of all the replies sent in response to them. And of course Google said it will address the spam issue through vigorous filtering methods.

Not to be confused with the GNOME mail client project that uses SQL-based vfolders, Gmail will compete with similar free offerings from Yahoo! and MSN, which runs the popular Hotmail service.

According Google founder Larry Page, the inspiration for Gmail came along because he and Google co-founder and president of technology, Sergey Brin realized search is number two online activity and checking e-mail is number one. The corporate legend goes that a Google user complained about the poor quality of existing e-mail services.

"She kvetched about spending all her time filing messages or trying to find them," Page said in a statement. "And when she's not doing that, she has to delete e-mail like crazy to stay under the obligatory four megabyte limit. So she asked, 'Can't you people fix this?'"

The company said Gmail is built on the premise that users should never have to file or delete a message, or struggle to find an e-mail they've sent or received. The problem was handed over to an unidentified Google engineer who worked on it in his off time. Google employees are encouraged spend a day a week on projects that interest them. A company spokesperson said Gmail would support external POP3 accounts.

Brin admitted that "developing Gmail was a bit more complicated than we anticipated," but the company is "pleased to be able to offer it." No formal release date has been announced.