The study shows that "commercial email servers" (which, in this study's parlance are well-configured, legitimate email servers that the study authors were able to identify as sending commercial messages), had an average 88% delivered (either to the inbox or to a junk or bulk folder), 9% rejected (meaning blocked at the gateway) and 9% filtered (meaning messages that are blocked after being run through the ISP's filters). Compare this to the set of all "legitimate" servers studied, which had an average 56% delivered, 8% rejected, and 19% filtered.
It's no small thing to achieve that delivery rate! Our messages must elbow out literally billions of other messages to get past the filters - and in fact, this high quality commercial email is just a fraction of the total that ISPs must manage. The study found that less than 20% of all email processed by the ISPs comes from a "legitimate" IP address - which means it is a real, static, well-configured email server. Most of the rest of it is horrible spam, phishing attacks, scams or from servers that have no business sending email at all.
Since the ISPs carry the full cost burden of sorting and filtering all those messages, they have some pretty stringent measures for determining which messages to let through and which to block. So if our email marketing messages look even a little like spam, they will get treated as such. And here is what is pretty shocking: it doesn't take much at all to look like spam.
In fact, the study found that legitimate commercial servers with even one spam trap hit saw their deliverability rate plunge to 38% versus 58% for servers with no spam trap hits. Similarly, IPs that appeared on even one of the top nine public blacklists had a deliverability rate of 35% versus 58% for mailers not listed on any of these blacklists. It doesn't even seem to matter if the blacklist is being used by the ISP in question- some of the blacklists tracked in the study are not widely used by ISPs. But the patterns of behavior that cause that server to be blacklisted also cause them to be blocked.
This deliverability pattern held true for unknown user rates as well. IPs with an unknown user rate below 10% had an average of 67% of their email delivered; versus 44% for senders with dead email address rates greater than 9%.
With all that to contend with, you'd think that we email marketers would be able to rest if our messages successfully run the gauntlet of filters and prove their worth among billions of spam messages. Not true. This email ROI race is a marathon, not a sprint. Even if we reach the subscriber's mailbox, we have to still break through the dozens or hundreds of messages there to earn a response.
The good news is that the keys to success for both deliverability and response are well under the control of the marketer. In fact, the marketing pieces - all the things you do as a marketer to ensure a great subscriber experience like great content, relevant promotions, strong calls to action, and more -- are just as essential to great deliverability as the technical aspects like infrastructure, reverse DNS, bounce processing and authentication.
The bottom line: Messages from senders who are more welcome by subscribers are more likely to reach the inbox consistently, and drive a response or revenue. In fact, only messages that reach the inbox will consistently drive revenue. Deliverability is ROI.
The great, important weight of inbox deliverability is a shared responsibility between marketers and your tech team or your email broadcast vendor. It's also a huge opportunity - the study found that senders with a reputation-based Sender Score of 72 had, on average, delivered rates of 87%. Compare that to senders with a Sender Score of 26 who average a delivered rate of 23%.