Under the terms of the anti-spam law, spammers can face custodial sentences of up to five years, and fines ranging between $250 per unsolicited e-mail sent, up to $6 million in severe cases.

However, critics of the Act have suggested that by requiring the recipients of spam e-mails to opt out of receiving them, rather than obliging firms to receive permission before sending bulk mailouts, and by overriding some tougher laws put in place by state authorities, the federal legislation has actually made things easier for spammers.

Speaking to the IDG News Service this week, Laura Atkins, president of the SpamCon Foundation condemned the fact that CAN-SPAM does not allow individuals to take legal action against spammers, observing that:

"CAN-SPAM has not made it any easier to find spammers. It has not decreased the amount of spam."

According to IDG, this appears to be supported by figures released by manufacturers of anti-spam products, such as Postini, which recently revealed that the amount of legitimate e-mails that it sees has dropped from 22% at the beginning of 2004 to just 12% by the beginning of this month.

However, ISPs have used CAN-SPAM to file hundreds of civil lawsuits against spammers in 2004, Jennifer O'Shea, spokeswoman for Senator Conrad Burns (R-Montana), the main sponsor of CAN-SPAM explained.

"Senator Burns has said from day one that enforcement is key for this legislation to be effective," she argued, continuing:

"We have seen several big lawsuits, which have been helpful, but we need to continue to see more of these lawsuits in order to keep up with big time spammers and keep spam out of inboxes."