America Online will start charging businesses for the commercial e-mails they send to its users in several weeks and Yahoo plans to follow.

Both companies will still accept free emails but are offering the chance to pay to avoid their spam filters. By paying the fees, messages will not go through spam filters. They are guaranteed to arrive and will bear a stamp of authenticity.

AOL's certified e-mail system would require advertisers to pay $2 to $3 per 1,000 messages. The plan is optional though the company cannot guarantee that all non-certified e-mail with Web links and images will be delivered.

The optional charging plan is meant for organisations that send a lot of e-mail and do not want their messages mistaken for spam. Those who do not want to sign up will be able to send mail the old-fashioned way. AOL says The New York Times and American Red Cross have already signed up for the service.

The two internet giants are working with tech firm, Goodmail Systems, on the project. Yahoo has yet to decide how it will route paid-for emails.

Any business can apply for the program. Goodmail determines if applicants are legitimate companies with pristine e-mail standards. AOL has final approval. E-mail of approved companies will come with digital tokens recognized by AOL security defenses. AOL subscribers will still be able to block mail from certified senders by adjusting anti-spam tools on their accounts, AOL spokesman Nicholas Graham says.

Marketers affected by the plan call it e-mail taxation designed to create a new stream of revenue for AOL. "This will be painful for marketers in the beginning, but it is a positive step in forcing them to be more selective in who they e-mail," says Jupiter Research's David Daniels. "Many now just blast e-mail rather than target an audience."

Jupiter Research estimates that e-mail marketing is expected to jump 24%, to $1.1 billion, by 2010 from $885 million in 2005.

If successful, the plan could entice other Internet service providers to follow.