"Spam is so significant a problem that it threatens to undo much of the good that e-mail has achieved," Gates wrote in one of his periodic to customers.
Microsoft has become increasingly active in the antispam crusade, most recentlyagainst spammers it said were responsible for sending a collective 2 billion unsolicited messages to Microsoft addresses.
The company also hasand allowed MSN subscribers to .
Gates said in the letter that Microsoft researchers are working on other technological fixes, including "smart" spam filters for mailboxes that would continuously adapt to keep pace with the latest spam techniques.
"Deciding precisely where to draw the line must ultimately be up to the individual," Gates wrote. "However, a smart filter can learn from a user's personal preferences to create a unique, antispam immune system that is much harder for spammers to work around."
The next version of Microsoft's Exchange e-mail server software will also allow third-party software makers to create spam filters that can easily be plugged in to Exchange. "Our goal is to do everything we can to secure e-mail systems with servers that monitor and control the points of entry," Gates wrote.
Gates also called on technology companies, consumer groups and legitimate marketers to work together to develop guidelines for distinguishing between commercial and personal e-mail, so businesses and individuals can more easily sift out the messages they want to receive.
And he applaudedin tackling spam, saying industry efforts need to be accompanied by strong punitive measures for spammers who continue to bombard businesses and consumers. "Self-regulation needs to be supported by strong federal legislation that empowers consumers without threatening the vitality of legitimate e-commerce," Gates wrote.