Hotmail sets email limits in spam-busting bid

Microsoft's MSN Hotmail has tightened restrictions on daily outbound messages sent by subscribers, a tactic it says will help curb spam.

The company on Friday said that Hotmail subscribers are now limited to sending only 100 messages a day. It is "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 one per cent 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 per cent of Hotmail users would find this new limit perfectly acceptable," she said.

Imposing rate limits on email usage is fairly common among internet service providers as a way to stop bulk messages before they're carried 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 an anti-junk mail mission recently, as the amount of it bogging down email networks and subscriber inboxes has grown to outlandish proportions. (ISPs estimate that it has risen by more than 500 per cent in the past 18 months.)

The company, which has nearly 120 million email 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.

The company is also getting litigious over spam. In the past month, it sued in US federal court to learn the identities of some spammers, and it has promised to pursue similar suits. Both AOL and EarthLink have won monetary damages in suits against spammers.

Margie Arbon, director of operations of 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 are unwittingly helping junk mailers shuttle 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 ISPs' customers are spamming, but this does prevent problems. Really if you're dealing with a free service and if you have the need to run that kind of volume of email you probably should be looking at some paid-for service," she said.

One Hotmail member said that he noticed the rate changes last 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 email to his contacts.

"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 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.

Stefanie Olsen writes for News.com