Two years ago, right before Carly Fiorina took the helm at Hewlett Packard [Ad by Coupon Companion] , its Web site was rated one of the worst on the Internet: HP was known for its focus on equipment, not customers. Last January, to improve its relationship with clients, HP sent e-mail newsletters to all customers who registered online. It gave new customers incentives like better warranties to register via its Web site. Implementation of the campaign was left to Digital Impact Inc., a Silicon Valley e-marketing company.

Digital Impact segmented HP’s customer e-mail list by date-of-purchase and product, and sent customized newsletters containing information about optimizing the performance of HP products [Ad by Coupon Companion] and services, including reminders about maintenance.

Here’s the cool part: The newsletters featured a button allowing readers to forward it to friends or colleagues. The user clicks and sees a Web page hosted by Digital Impact for HP, where they can type in the friend’s e-mail and a comment, then hit the send button,” explains Wiebke Sinzliu, business-to-business engagement manager for Digital Impact. The technology takes the message, inserts it above the newsletter, and e-mails the whole thing to the friend.”

At the bottom of each newsletter readers are asked if they’d like to receive HP newsletters themselves. If so, they can sign up [Ad by Coupon Companion] , adding their name to HP’s database.

Though HP’s marketers may not have realized it, having its customers send newsletters to friends or colleagues is textbook viral marketing [Ad by Coupon Companion] , one of the newest, cheapest ways of marketing on the Web. It involves creating an e-mail so compelling either graphically or by using an incentive that customers want to pass it along. And when e-mail comes from a friend, the recipient is much more likely to open and read it.

Hewlett Packard’s goal with this campaign was to drive consumers to its Web site and ultimately to increase sales. Viral success is measured in click-throughs how many readers clicked on the teaser of a newsletter article, hooked into HP’s Web site, and read the full article.

For those on our original list, the click-through rate was ten to fifteen percent,” says Sinzliu. For those who received it from a friend or colleague, it was between twenty-five and forty percent.” HP’s numbers mirror the national statistics for viral marketing [Ad by Coupon Companion] . Industry analysts say between 5 percent and 15 percent of those receiving viral messages follow the links. The reason for the higher numbers among those receiving messages virally is that the audience is prequalified.

This is true especially in the b-to-b arena,” Sinzliu says. Often someone sends it to a colleague after they’ve talked about something similar, perhaps in connection with a work-related problem.”