The Redmond, Wash.-based company on Friday said that Hotmail subscribers are now limited to sending only 100 messages a day "in an effort to prevent spammers from using Hotmail to spread spam," said Lisa Gurry, MSN lead product manager. The change, made last week, should affect only about 1 percent of its nearly 110 million worldwide users, based on historical usage data, Gurry said.
"The higher the limit is, the more likely that the service can be used for spam, so we found that 99 percent of Hotmail users would find this new limit perfectly acceptable," she said.
Imposing rate limits on e-mail usage is fairly common among Internet service providers as a way to stop bulk messages before they're ferried on their networks, anti-spam advocates say. But as effective as it can be to trip up potential spammers, it can also occasionally frustrate legitimate mailers who may be sending, for example, a party invitation or political message to friends. Other Web-based mail services, including Yahoo, also have outbound rate limits.
MSN has been on a tear of late fighting junk mail, as the amount of it bogging down e-mail networks and subscriber inboxes has grown to outlandish proportions. ISPs estimate that it has risen by more than 500 percent in the past 18 months.
The company, which has nearly 120 million e-mail customers through its Hotmail and MSN Internet services, has bolstered internal tactics to thwart spam in recent months above and beyond employing third-party software to filter junk. These include operating an internal "blocklist" of known spammers whose mail should be barred from customer in-boxes.
In one fluke extreme, the company recentlyof Internet Protocol addresses from AOL Time Warner's RoadRunner broadband service and EarthLink on its blocklist for several days. As a result, messages sent from EarthLink and RoadRunner subscribers would not get through to their intended MSN recipients.
MSN is also getting litigious over spam. In the past month, it sued in federal court to learn the identities of some spammers, and it hassimilar lawsuits. Both AOL and EarthLink have won monetary damages in suits against spammers.
Margie Arbon, director of operations of antispam group MAPS, said that rate limits are a step in the right direction because they can cut off spam before it's sent. For mail providers and their customers, enacting rate limits also helps to inadvertently prevent computers that may be infected with a spam virus from being used as an open port to relay junk mail, she said.
An alarming number of people areshuttle spam by running software meant to allow multiple connections over a LAN (local area network) to the Internet through a single line, or what's known as proxy servers. Many proxy servers are installed insecurely, and spammers have discovered tricks to tap into them to send junk mail with little trace.
"We need to be able to stop this at the source before it gets on the network," Arbon said. "Not to say that any ISP's customers are spamming, but this does prevent problems. Really if you're dealing with a free service and if you have needs to run that kind of volume of e-mail you probably should be looking at some paid-for service."
One Hotmail member said that he noticed the rate changes Tuesday, when a window popped up warning that he was exceeding his outgoing message limit for a 24-hour period after trying to send a political e-mail to his contacts. At least one source said Microsoft lowered the number of outbound messages it allows from 500 to 100.
"The only restrictions that Hotmail had in the past was to limit to 50 the number of contacts that could be mailed at once. Therefore I always split my list in half and sent the same message twice," he said.
"To circumvent that I now have to painstakingly paste together multiple messages...or wait for another day."
For its part, Yahoo uses several tactics to fight spam, including its proprietary filtering system that was recently updated. The company said it enforces a "rate limit designed around typical usage patterns of spammers" but would not disclose details of the limits.
MSN and Hotmail use spam-filtering software and services from San Francisco-based Brightmail, whose techniques focus on the message's content when filtering spam. Beyond that, MSN's spam-abuse team compiles its own list of IP addresses that are known to generate unsolicited junk messages, and it blocks all messages from them.
Ray Everett-Church, chief privacy officer for Philadelphia-based consultancy the EPrivacy Group, said that instant messaging networks also use rate limits to stop people from bombarding chat rooms with spam-related instant messages.
"Some users also try to use e-mail accounts in ways that the account didn't intend, such as running a business mailing list from a consumer e-mail account," he said. "The volume restrictions are common to help avoid having people using accounts in ways they were not intended."