Web E-Mail Services Battle Spam, and One Another Hotmail is really proud of its spam-stopping capabilities. As part of an effort to reverse a well-earned, but dated, bad reputation for spam-heavy e-mail inboxes, Hotmail, the world's largest Web e-mail provider, hired the consultancy Cascade Insights to hold a contest ranking the spam-stopping abilities of the big three Web e-mail providers. The test results, which are scheduled to be released Monday, put Microsoft's Hotmail on top but almost tied with Google's Gmail, while Yahoo Mail was a distant third. In 2009, Cascade ran the same study and ranked Gmail first, followed by Hotmail. To compare the services, Cascade set up e-mail accounts using the same username at each service and "seeded" those addresses in identical ways: It posted them on public blogs and Facebook pages and signed them up for things at a large group of Web sites, among them debt-help, singles and pirated-content sites. Then it watched the accounts for five weeks to see what happened. Spam happened. In the Hotmail account, 48.57 percent of e-mails in the inbox were spam, slightly less than the 48.88 percent in the Gmail inbox. Yahoo Mail was third with 58.33 percent. The remainder of the e-mail found in the inboxes was what Cascade calls "ham," or newsletters and other legitimate commercial messages resulting from opting-in to various services. Provided with a description of the study, Yahoo said in an e-mailed statement that spam rates found by Cascade "seem very high. In practice, we see that 99 percent of all spam is blocked before ever reaching the user's inbox. In this study, the vendor [Cascade] simulated user behavior and editorially determined what is spam, so it's possible the methodology influenced the results. Yahoo said it had achieved a 60 percent improvement in spam blocking since it introduced the latest version of Yahoo Mail in May 2011 and blocks 600 billion spam messages a month. It said it came in first in a 2010 spam test conducted by the Fraunhofer Institute. Google said that powerful spam protection was among a main reason that people use Gmail. "We are constantly improving our spam detection technology, and our internal data indicates it is stronger than ever," the company said in a statement. "Factors such as false-positives - mail that is incorrectly labeled as "spam" - and filtering that keeps spam from ever reaching a user's inbox or spam filter, are harder to measure in external studies by other companies." Microsoft said Hotmail's rise in Cascade's rankings showed that the bad old days of 2006 are well in the past. Back then, about 30 percent of mail in the average Hotmail inbox was spam. Complaints were rife and people were abandoning the service. But Hotmail moved to fix the problem. It added several hundred engineers and developed a major feature called SmartScreen, which also blocks phishing and malicious attacks. Spam's share of Hotmail inboxes was 5 percent as of last year and, today, is below 3 percent, Microsoft said. The anti-spam push dovetailed with a broader Microsoft effort to alleviate security issues that plagued its Windows operating system and continue to mar its reputation, although its security is now considered industry leading by many experts. "Hotmail, in all honesty, had just gotten behind in the game" against indefatigable spammers, said David Law, director of product management for Hotmail. Because we were at a high level in 2006, I think Hotmail probably suffers from some misperceptions that linger from those days. He added, "I think when people see the study, they'll be surprised." Mr. Law said Hotmail tackled two major areas: blocking spam from entering inboxes and stopping spammers from using Hotmail to send spam. Filtering in both directions was enhanced with better tools for recognizing spam content and patterns. Today, Hotmail filters out more than a billion spam messages a day. It also stepped up its use of reputation to weed out potentially bad actors, building a database of I.P. addresses that it could block messages from. In fact, all of the Web e-mail services have made major strides against spam. Their efforts have most likely contributed to an overall decline in spam volumes to about 75 percent of all e-mail from highs around 90 percent. More improvements are on the way. The big three and other e-mail providers recently announced they are working together to develop a technology standard called DMARC that will let e-mail senders prove they're legitimate. Doing so will allow e-mail services to block fraudulent spoofed messages, especially phishing messages, more reliably. But don't expect the competition to ever ease up. "We're starting to see some real momentum with people coming to Hotmail, particularly from Yahoo," Mr. Law said. We definitely have a confidence we haven't had in a while.