The majority of email marketers are failing to ensure their campaigns are being successfully delivered to their intended audiences, it has been revealed.

According to director of online safety for Microsoft Craig Spiezle, firms are running the risk of their advertisements being barred as users look to block out increasing numbers of spam and virus-laden emails, reports Multichannel Merchant.

He claimed: "The rules of deliverability have changed dramatically and marketers who are working on content filtering alone may not be getting their email delivered."

Mr Spiezle recommended that advertisers should use a different IP address to target specific emails to those users who have opted into services offered by a company compared to those who have signed up to receive emails from a third-party or affiliate list.

He adds that marketers may also find their campaigns blocked if they send out too many emails.

Meanwhile, as ISPs increasingly analyse the reputation of email marketers when deciding whether to block messages, Mr Spiezle claimed "if you're working on the old paradigm of 'hey, I've got good content, so I'll get through,' that won't necessarily lead you to success".

An E-consultancy study revealed that 47 per cent of British email marketers fail to track return on investment made by their advertising campaigns.