Sender Reputations Have A Strong Impact on Email Performance. Here’s How.

May 23, 2018

This article is included in these additional categories:

Customer-Centric | Digital | Email | Privacy & Security

Email providers are increasingly making life difficult for spammers, as just one-quarter of emails in 2017 came from the least reputable senders, down from 60% of messages in 2012. That’s according to Return Path, which has released its latest benchmark report on the state of email reputation.

In 2017, more than one-third (36%) of the messages analyzed were sent by the most reputable senders, being those with a Sender Score above 90. Sender Score is Return Path’s free reputation calculation service, and it carries a 0-100 rating. To arrive at its conclusions, Return Path analyzed more than 6 trillion emails sent last year from IP addresses whose Sender Score was calculated, and whose subscriber engagement and inbox placement data were available for analysis.

Which Metrics Affect Sender Reputation?

There are three main metrics that affect sender reputation, according to Return Path: complaint rate; unknown user rate; and spam trap count.

Complaint Rate

Senders with a reputation score of 91 and higher averaged a complaint rate (where the recipient marks the email as junk or spam) of just 0.5%. That was markedly below the range for other Sender Scores, with the least reputable senders (a score of just 1-10) averaging a dismal 7.4% complaint rate.

The gap between senders with better and worse reputation scores has also widened: those with higher scores achieved lower complaint rates in 2017 than in 2016, while those with lower reputation scores had higher complaint rates in 2017.

Unknown User Rate

Email list quality also impacts reputations, per the report. Unknown users are email addresses that never existed, have been terminated by the mailbox provider or abandoned by the mailbox user. Senders that maintain a high rate of unknown users in their database are perceived to have poor list hygiene, which affects their reputation.

Indeed, senders with the best reputation (91-100) kept clean lists last year, averaging an unknown user rate of just 1%. By comparison, senders with scores of 50 or below had an unknown user rate that was 5-8 times higher.

Spam Traps

Return Path notes that spam traps are email addresses that don’t belong to active users and are instead used to find spammers and senders with poor data quality practices.

Interestingly, spam traps were more frequent last year than in 2016 across sender score bands. There was a huge difference between those with the best and worst reputation scores: senders with a score of 91-100 averaged just 0.36 spam trap hits, compared to an astounding 7.53 traps hit by senders with a reputation score of 1-10.

Mailbox Providers Turn Away Messages from Low-Reputation Senders

Sender Score appears to be strongly correlated with the Averaged Delivered Rate, meaning that mailbox providers’ gateway filters are often bouncing or rejecting messages sent by mailers with lower reputation scores.

The results indicate that senders with a score above 90 (91-100) had an average delivered rate last year of 91%, meaning that 91% of their messages were not bounced or rejected by mailbox providers’ gateway filters. (This particular analysis does not identify what percentage of emails reached the inbox.)

The Average Delivered Rate dropped to:

  • 68% for senders with a score of 81-90;
  • 42% for those with a score of 71-80;
  • 24% for those with a score of 61-70; and
  • 15% for those with a score of 51-60.

Senders with a score of 1-10 averaged a delivered rate of just 1%!

Which Mailbox Providers Are the Most Lenient?

Given Yahoo’s troubles, it may not be too surprising to see that senders with low scores have an easier time reaching Yahoo inboxes than Gmail or Microsoft inboxes. But it’s actually AOL inboxes that are the easiest to reach for spammers.

Consider that senders with reputation scores as low as the 11-20 band still achieved inbox placement rates exceeding 80% (the global average) for AOL addresses.

By comparison, just 72% of emails sent by mailers with the highest sender band (91-100) made it into Microsoft inboxes last year. Microsoft was the most difficult mailbox provider to reach last year.

Meanwhile, 81% of emails sent by those with the highest sender band reached Gmail inboxes. But fewer than half sent by those with scores of 70 or less made it to Gmail inboxes, as did just 8% of those sent by the lowest-reputation senders.

The full report can be viewed here.

For more on email deliverability, see these recent articles:

About the Data: Return Path describes its methodology as follows:

“To conduct this study, Return Path analyzed over 6 trillion messages sent during 2017 from IP addresses whose Sender Score was calculated, and whose subscriber engagement and inbox placement data were available for analysis. In addition to Sender Score data, this report used data from the Return Path Reputation Network to track inbox placement rates across mailbox providers, and the Return Path Consumer Network to identify the Sender Score and inbox placement rates of more than 17,000 commercial senders. Data used for this report is aggregated and anonymized, and is not limited to Return Path clients. Sender Score is a free reputation calculation service and is available at”

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