Eighty Percent of Email is Being Sent From Illegitimate or Unknown Mail Servers

Commercial Mailers With Low Unknown User Rates and No Spam Trap Hits Have Delivery Rate Increases of More Than 20 Points

NEW YORK & DENVER–Eighty percent of email is being sent from illegitimate or unknown mail servers, Return Path discovered with its new Return Path Reputation Benchmark Report. Return Path found that forty-six percent of email is being sent from hosts that should not be sending email at all – compromised hosts, dynamic IP addresses, and other non-mail servers. In addition, 34% of email is sent from “unknown” IPs which are not classifiable by available data.

Return Path conducted the Reputation Benchmark study by examining a sample of 2.3 million IPs pulled from the Return Path Reputation Data Network – a cooperative data network that collects and analyzes email data from more than 20 ISPs and other data providers representing more than 100 million mailboxes.

For the study, Return Path removed the data from servers that do not have reverse DNS and are clearly not supposed to be sending email. If you factor in the 35% of servers with no reverse DNS, the “bad” mail hosts goes even higher with 87% of email being sent from mail hosts that should not be sending email.

Return Path found a quantifiable link between deliverability success rates and the quality of the server that email is sent from. Email sent from legitimate email servers averaged 56% delivery rates, 20% rejection, and 8% filtered. Email sent from servers that were identified as illegitimate had average rejection rates of 60% and delivered rates of 23%. Illegitimate hosts actually had low filtered rates – slightly less than 1% on average. While this may seem counterintuitive, it actually makes perfect sense – email coming from illegitimate sources is easy to identify and reject. Contrast these rates to email sent from unknown hosts which averaged 45% delivery rates, 5% filtered rates, and 35% rejection rates.

“The Reputation Benchmark quantifies the impact of IP reputation on the deliverability of the messages coming from that IP,” said George Bilbrey, GM of Delivery Assurance, Return Path. “Clearly, email best practices matter. If you’re sending commercial email from a legitimate mail server, your email has a better chance to reach consumers’ inboxes. Commercial senders need to be vigilant about all aspects of email sending, including infrastructure, list hygiene and the value of their messages to recipients.”

In fact, the Reputation Benchmark study quantified the negative impact for commercial senders who hit spam traps or have high unknown user rates. (Spam traps are defunct email addresses that ISPs use to identify spammers.) IP addresses categorized as legitimate commercial servers with even one spam trap hit saw their delivery rate plunge to 38% versus 58% for mailers with no spam trap hits. For unknown user rates, the report found that servers with unknown user rates below 10% had 67% of their email delivered, on average, versus 44% for senders with dead email address rates greater than or equal to 10%.

The study also found a relationship between the servers Sender Score rating and its delivery rates. Sender Score is based on data contributed by ISPs and other receivers of large volume email which is then consolidated and analyzed by Return Path to provide all stakeholders with a simple-to-understand email reputation measure for almost any IP sending email today. The study found that servers with a Sender Score of 72 had, on average, delivered rates of 87%. In contrast, IPs with a Sender Score of 26 had an average delivered rate of 23%.

“The easiest and most effective way for commercial senders to know their email sending reputation with ISPs, a reputation that includes whether or not they’re sending email from legitimate IP addresses, is to know their Sender Score. A higher Sender Score means a better reputation which correlates to improved deliverability rates for their emails. While a lower Sender Score indicates a poor reputation and lower email deliverability,” Bilbrey said.

Return Path offers free access to our Sender Score to any sender, receiver or consumer of email at their reputation portal: www.senderscore.org.

About Return Path
Founded in 1999, Return Path is an email performance management company dedicated to helping its clients build better relationships with their customers, generate higher response rates, and achieve significant returns on their investments from their email programs. More than 1,500 companies currently use Return Path’s services to generate superior results from their email programs, taking advantage of Return Path’s pioneering innovations in deliverability, email list quality solutions, customer acquisition, online market research, and best practices strategy. For more information, please visit www.returnpath.net.

Return Path
Tami M. Forman, 212-905-5500 ext 205
tami.forman @ returnpath.net

Jeff Rutherford Media Relations
Jeff Rutherford, 413-369-4128
jeff @ jeffrutherford.com

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