Ben Johnson has been sending email for months from his Hotmail account. But he just discovered that some of his messages were diverted to the trash, before arriving at their destination. Johnson, 24, is among the millions of customers caught in the crossfire of a battle over spam. For at least five months, some Hotmail customers' outgoing mail has been blocked. In an apparently overzealous attempt to prevent spam, Microsoft's Hotmail has been discarding email sent to and from sites hosted by controversial Internet service providers--even if the sites themselves were not controversial. What's more, Hotmail didn't tell people that some outgoing mail was being discarded. Instead, it said the error was because of a problem connecting to the recipient--a practice that has particularly alarmed some customers. "If Microsoft, one of the largest technology companies, can say who we send email to, that really puts constraints on freedom of speech in the US," said Johnson, an information technology worker at a major Illinois hospital. Microsoft defended its actions, saying it's only trying to prevent spam. "MSN has been very aggressive and proactive in protecting our MSN Hotmail users from spam," Sarah Lefko, MSN product manager, said in an email, noting that the company will review blocked sites on a case-by-case basis, if a complaint is filed. The quagmire illustrates the challenges of trying to prevent spam, while preserving free speech. After all, no one wants an in-box crammed with unsolicited porn, and bogus plans to work from home for millions of dollars. Email services are struggling to find a fair way to prevent that from happening. Still, to subscribers such as Johnson, the practice of blocking outgoing mail is extreme. "It's like killing a fly with a shotgun," he said. The controversy stems from Hotmail's membership in the Mail Abuse Prevention System (MAPS), an organization formed to crack down on spam. MAPS is the keeper of the Realtime Blackhole List (RBL), a list of ISPs known to host some major spammers. However, many of those ISPs also host sites that don't send spam, and those sites often are blocked, too. MAPS hopes the practice will convince legitimate sites to abandon hosts that cater to spammers. For example, ISP Media3 Technologies is listed on the RBL because it hosts half a dozen spammers. However, it also hosts sites such as Peacefire.org, which alerted members this week that Hotmail users have been unable to reach it for five months. After Peacefire protested, mail to the organisation was allowed to continue, earlier this week. Other companies besides Hotmail also may be blocking outgoing mail, but because they don't always notify customers, it's difficult to determine whether it's happening unless someone complains. When a company signs onto MAPS, it has several options to control spam. It can use a method that compares each incoming message with a list of ISPs on the RBL. Or it can choose another, more sweeping approach that blocks email, both incoming and outgoing, at the network borders. Companies also can tailor their systems to block only certain sites or just incoming mail. Hotmail apparently chose the most restrictive method. Kelly Thompson, MAPS' RBL project manager, said most companies choose the least severe technique. Thompson acknowledged that blocking outgoing mail might be a little extreme, but given the huge load of spam that major services such as Hotmail must deal with, "they have the right to be as strict as they want." The idea behind blocking outgoing mail is to ensure that people don't reply to spammers, who often offer recipients a fake option of unsubscribing from their list. Instead of removing people, spammers use the incoming messages as a signal that an email address is an active one where they can send more spam. Still, Web-based email users are angry. Kyle McCowin, a 21-year-old student, first learned of the blocks when he was alerted by Peacefire earlier this week. He said he could understand blocking incoming mail, but the move to block outgoing mail disturbed him. "I was caught completely by surprise," he said. "As far as I'm concerned, there's no need to block outgoing mail." McCowin also wishes Hotmail had made it more clear that it was discarding some of the messages he sent. "They just sort of pocket the email and don't even tell you about it," he said. Microsoft ran into a similar spam-related problem three years ago when it tried to block unwanted emails by filtering out incoming messages from Outlock 98 that contained certain phrases or grammar, such as a string of exclamation points or the words "for free." As a result, many people found that they never received messages from friends who were fond of multiple punctuation marks. MAPS already has stirred plenty of controversy in its attempt to balance free speech rights with spam control. In August, the organisation was sued by Harris Interactive, which claimed it was being unjustly blocked. The suit was later dismissed. ISPs Exactis and Media3, which hosts Peacefire, have filed similar suits. Media3 lost the first round in its court battle January 2, when a federal judge in Boston denied the company's request to be taken off the list. Take me to ZDNet Enterprise Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.