Yahoo, which has marketed itself as a successful spam fighter for e-mail users, said most of the new functions are available only to subscribers of its Mail Plus service, which costs $29.99 a year.
The battle against spam has drawn the attention of e-mail providers and legislators, amid growing concern about the cost of junk e-mail to companies and consumers.
Yahoo said it has seen a 40 percent jump in spam from January to August and now averages 700,000 spam reports a day. Some analysts estimate that spam totals one-third of all e-mail, costing corporations billions of dollars a year.
Yahoo said its new AddressGuard feature would let users create a fictitious “base name” and then 500 variations on that name that they could give out when shopping, banking and joining communities online.
If an address started to receive spam, the user could simply shut down the address and use another one.
SpamGuard Plus, which like AddressGuard is available only to premium subscribers, lets customers set individual rules to define spam and continue to use a blanket filter to block all spam.
Another new feature available to all users allows for a message display limited to e-mails from known users. Some users will start to have that function next week, Yahoo said, though it will not be fully launched systemwide until November.
Yahoo has also changed rules on viruses, forcing users to scan all attachments for viruses before downloading. Such scans had been optional.
Brad Garlinghouse, vice president of communications products at Yahoo, told Reuters the company had to keep enhancing its software because the legal battle against spam could not do the job alone.
“Legislation and litigation, it’s something of a whack-a-mole problem,” he said, a reference to a popular arcade game that challenges players to try to hit an increasingly fast array of pop-up figures, though he added Yahoo has supported spam laws and used anti-spam suits in past.
Yahoo said its marketing research highlights the extent to which spam is despised. In an August survey of Yahoo users, 77 percent said they would rather clean a toilet than sort through the junk e-mail in their inbox.