15 Jun 11: On average, around one fifth of all marketing emails are being blocked by ISPS, according to the latest research across more than 18 million IP adresses from Return Path. Emails that senders believe to be delivered are hitting spam traps, attracting complaints and being sent to unknown users - all of which are killing their sender reputation with ISPs.

The 'Sender Reputation Report: Key Factors that Impact Email Deliverability' advises marketers on how ISPs make decisions on which emails to block, how sender reputation affects inbox placement and best practices to achieve higher inbox placement.

Return Path's Sender Score www.senderscore.org enables marketers to measure their IP's sender reputation ranking for free. A low Sender Score rating (41-50) means guaranteed low inbox placement rates (as low as 64%).

 “If you have a million addresses and 20% of your emails are blocked, you are missing 200,000 messages every time you hit ‘send,’” said George Bilbrey, President of Return Path.  “This means lost revenue, poor customer experience, increased customer service costs, lost branding opportunities and the inability to advance your message to your marketplace.  By understanding the impact email reputation has on email programs, marketers can take immediate and corrective action to ensure higher inbox placement rates.”

The study can be downloaded in full here.