Around half of emails sent are spam, and this figure is set to rise to 60 per cent by mid-2004, industry experts have predicted.

Analyst Gartner has warned marketing firms to take immediate steps to differentiate their marketing messages from spam if they want to be succesful with email campaigns.

Gartner said that by 2005, content managers, rule-based software and ISPs will effectively blacklist 80 per cent of all email marketing campaigns, including permission-based email.

But for marketers the pressure to cut costs outweighs consideration for the email's usefulness to customers, said Gartner industry analyst Adam Sarner.

"Before customers ignore this valuable medium, marketers must start again by clearly identifying their customer base, surveying their customers as to the types of email they would like to receive, and then deliver on the feedback and give customers a way to update their preferences frequently," he said in a statement.

According to Gartner, email marketing can be an effective communication tool, with a well-crafted email receiving a response rate of as high as 15 per cent, compared with less than one per cent for banner ads.

"Because email can be effective and is less expensive than traditional marketing methods, by the end of 2004 more than 80 per cent of companies engaged in direct marketing will conduct at least one email marketing campaign," added Sarner.