Microsoft Corp. said Wednesday it has adopted an e-mail "whitelist" program by IronPort Systems Inc. that will allow legitimate marketers to thread the gauntlet of spam filters protecting its inboxes.
Microsoft's Hotmail and MSN e-mail services, which together claim 170 million regular users, will require marketers to put money up front if they wish to ensure their messages aren't mistaken for unwanted spam.
IronPort's "Bonded Sender" service guarantees that legitimate marketers who post a cash bond and adhere to a set of guidelines will get their messages delivered.
"It's the exact opposite of blocking. It says, 'Hey you're a good guy, I'm not going to run you through the metal detectors," said Tom Gillis, IronPort's vice president for marketing.
Such a "whitelist" approach requires the active cooperation of marketers -- a much more likely prospect now that Microsoft has signed up, Gillis said.
Unsolicited bulk messages now account for roughly two-thirds of all e-mail, according to several estimates.
Internet providers use filters to examine incoming messages and consult "blacklists" to block traffic from computers known to send out spam.
IronPort's approach rewards e-mail senders who agree to be held accountable for their messages.
Participating marketers must demonstrate a history of responsible e-mailing and must provide an easy way for consumers to opt out of future mailings, among other things.
Those found to be engaging in abusive behavior forfeit a cash bond of up to $20,000, Gillis said.
Internet providers are considering other ways to make e-mail more reliable. Both Microsoft and Yahoo Inc. are developing authentication systems that could make it harder for spammers to appropriate others' e-mail addresses.
Other methods would make spamming less profitable by sucking up computing power or requiring human input every time a message is sent.
"When you add these up over time, it will be uneconomical to send out spam," said Microsoft spam specialist George Webb.