Marketing: How to combat low email deliverability

21st Oct 2016

45 years on and email is firmly established as part of today’s communications. The recently published Econsultancy Email Industry Marketing Census reports that email beats all other channels hands-down when it comes to generating ROI – 73% of respondents scored email as “Excellent” or “Good” in this regard.

However, spam still plagues the medium. While modern spam filters do an excellent job of keeping junk out of people’s inboxes, many organisations are caught in the crossfire of this ‘war against spam’ when their legitimate emails end up in the spam folder as false positives. According to Return Path’s Deliverability Benchmark Report, an average 1 in 5 permission-based marketing emails currently fail to reach the inbox.

Downward trending deliverability rates represent an opportunity cost for marketers. Each non-delivery is a failure to promote goods/services, build valuable relationships and – ultimately – generate profits for the sender’s business. But it takes far more than just hitting the 'send' button, and many senders are still operating blind when it comes to measuring and managing this important email KPI.

To get a better view of their programme's deliverability, marketers firstly need to understand the difference between delivery and placement. The former is effectively emails sent less emails bounced, and is the metric most email platforms report against. However, this metric provides no insight into where the emails are being delivered – inbox or junk?

Measuring inbox placement is slightly more tricky, but marketers do have several options available to them:

  • Operate a set of test accounts for each of the major mailbox providers so they can see for themselves what happens to the emails they are sending.
  • Use a seed list, where a set of seed addresses are representing hundreds of global mailbox providers and filters generates deliverability reports for each campaign.
  • Monitor inboxes through a consumer network. The difference here is that data is generated from real email accounts, actively owned and managed by subscribers at AOL, Gmail, Outlook and Yahoo, enabling actual email behaviour to be collected.
  • Other email KPIs such as opens and clicks can also be used as a proxy for deliverability performance – an unexpected decline in these metrics may point to reduced inbox placement rates.

Once you are measuring, management becomes easier! Marketers who are looking to boost their deliverability should focus on four key areas: acquiring and maintaining quality subscriber data; broadcasting from a solid infrastructure; building and maintaining a positive sender reputation; and increasing positive subscriber engagement metrics (plus reducing negative ones!).


An unclean list has severe consequences for deliverability. Invalid addresses, spam traps, and even inactive accounts will all impact sender reputation and deliverability metrics, and may potentially result in blacklisting. Email programmes should validate new addresses at point of entry, and employ a robust permissioning model such as confirmed opt-in or double opt-in.

Programme owners should also be thinking about how to persuade their new subscribers to provide their primary email address. This is the address that they use most frequently, and contains their personal correspondence, as well as marketing emails from their favourite brands. Research from Return Path has shown that 83% of all email opens are generated by primary addresses. Subscribers are more likely to provide their primary address when they trust the sender to use it properly – setting clear expectations, making a strong “no third party share” promise, and providing options for subscribers to set preferences all promote higher levels of trust.


All of the major mailbox providers now expect email programmes to operate some form of authentication such as Sender Policy Framework (SPF) or DKIM (Domain Keys Identified Mail). These techniques basically confirm the emails are originating from trusted IP addresses that have been authorised for use on behalf of the sender. Failure to use authentication will generally result in emails being blocked or routed to the junk folder. Gmail has taken this one step further, and emails that fail to authenticate now have the avatar/logo replaced by a large red question mark.

More recently we have also seen the introduction of Domain-based Message Authentication, Reporting & Conformance (DMARC) which builds on SPF and DKIM by adding a reporting function that allows senders and receivers to improve and monitor protection of the domain from fraudulent email.

Building and maintaining sender reputation

All email programmes generate sender reputation metrics. The metrics combine to form a score which can be thought of like a barometer for the overall health of the programme. According to Return Path’s recently published 2016 Sender Score Benchmark, programmes with a score between 91-100 will be generating average Inbox Placement Rates (IPRs) of 95%, while programmes with a score between 71-80 will only be generating average IPRs of 76%.

Marketers can look up their sender reputations for free at

There are many different elements that combine to determine your sender score - although list hygiene, complaints, and spam traps are some of the most important ones. Operating good data management practices to quickly suppress opt-out requests, complaints, hard bounces, and non-responders will go a long way toward ensuring a healthy sender reputation.

Subscriber engagement

More recently, major mailbox providers like Microsoft, Yahoo, AOL and Gmail have also been considering inbox engagement metrics to provide an additional view of whether senders should be seen as good or bad actors.

These metrics include: messages read, messages forwarded, messages replied to, messages marked as 'not spam', messages marked as spam and messages deleted before reading. Marketers who generate higher levels of positive engagement from their subscribers are more likely to reach the inbox. Those who generate low or negative engagement from their subscribers will be more likely to find their emails landing in the spam folder. 

Marketers need to consider how to optimise how to harness positive inbox behaviours (e.g. organic forwards) while minimising negative behaviours (e.g. deleted unread) as part of their expanding deliverability strategies.

Guy Hanson is chairman of the DMA Email Council and senior director, professional services international at Return Path.

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