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How to Avoid the Spam Filter and Maximise Deliverability

There is nothing worse than setting up your collection launch email after months and years of growing your list of customers and subscribers, only for it to land in the spam filter, or even worse, not be delivered at all. I’ll run through what email deliverability is, why it matters, and how you can prevent your emails from landing in spam.

 

What is deliverability?

Email deliverability is ensuring your emails land in users’ inboxes and avoid the spam filters. 

Over 50% of all email traffic is spam content, that is, emails sent to people who didn’t ask to receive emails from the sender. Inboxes like Gmail, Hotmail, Outlook, and others have developed algorithms that filter out the emails that people didn’t ask for. Understanding the things these algorithms look for can help you land in customers’ inboxes. 

Many of the biggest brands neglect deliverability.  Even brands that have permission to send to users can, and do, neglect email best practices. In fact, larger brands are more at risk of landing in spam filters since they send larger volumes of emails and are at risk of the algorithms mistaking them for a malicious impersonator. 

Jay Jays - example of an email that has been marked as spam

An email from Jay Jays was marked as spam because they regularly use spammy words in their subject lines.

Marketers need to consider deliverability in every element of their email marketing; list growth, segmentation, automation, and design. I’ll run through everything marketers should consider to make sure your emails land in your subscribers’ inbox. Email deliverability isn’t just something you need to think about when you have a problem, it’s something you need to consistently maintain and nurture. 

 

Is it going undetected?

One of the challenges of detecting deliverability issues is that each inbox service has their own sender reputation score and scoring system. You may not realise you have deliverability issues as they affect each inbox service one by one. For example, if Hotmail users make up 15% of your list, and deliverability issues cause your engagement with those users to drop from 20% to 5%, it will only mean a drop from 20% to 17.8% on your whole list. This is a comparatively small drop, but a deliverability issue unchecked will be harder to correct, and will eventually lead to issues with other providers.

The table below is an example demonstrating a drop in open rates that can be difficult to detect when you are only looking at the total list numbers in your email performance.

 

Email can become a failing channel for some brands if it is not being consistently managed. However, it should and can be a core pillar of predictable customer traffic and sales for all Ecommerce brands.

 

So how do we know when an email is landing in the spam filter?

We never know for sure if an email has landed in the spam filter for many users, however, we can tell from looking at the open rates over time, and on the open rate per receiving domains. If you see your open rates on Gmail (users with “@gmail.com” email addresses) are usually between 20-25%, and then drop to 10%, then emails are likely landing in spam filters so users aren’t seeing the emails and therefore are not opening them. Across the Email Marketing industry, marketers have been able to figure out what factors matter, and what factors don’t. 

 

How does an inbox decide to send an email to the spam filter?

The inboxes, such as Gmail and Hotmail consider a number of factors, but they keep them secret so senders don’t game them to get around them – similar to the Google search algorithm.  However, similar to Google’s search algorithm, marketers have run a lot of experiments and made observations that point towards the factors that spam filters look at. 

The main factors are: 

 – Sender reputation

 – Content

 – The sender’s IP address (this is determined by the sending service you use)

 – The senders domain

 – The senders email address (ie, “From: [email protected]”, vs “[email protected]”)

 – The content of the email

 – User engagement with your email

 – The volume of the email, (ie, are there 10 emails or 1,000,000 being sent at once?)

 

What is Sender Reputation?

Sender reputation is a secret score that inboxes like Gmail keep on senders of emails. The score keeps track of the behaviour of senders over time to see if the brand has a history of sending quality emails to consenting users, or poor quality content to acquired lists. The sender reputation is a combination of email factors over time. 

Each of these factors, over time, give the inbox services information that they need to track your sender reputation, and then, when an email arrives, they use the sender reputation and the factors of the email to decide if the email will go to the Inbox, the Spam filter, or not be delivered at all. 

 

How does sender reputation work?

You can think of it this way; an email needs to score 20 or above to land in the inbox, if it scores lower it will land in spam. If it scores lower than 10, it won’t be sent to the email address at all. 

If you have a sender reputation of 18, then all other factors must add +2 for your email for a score of 20 to land in the inbox. If you have a non-spammy subject line, send to an engaged list, and use live text, then you will likely land in the inbox. This will also boost your sender reputation, from 18 to 19, so that next time you are even better positioned. Over time, if you have followed best practice for months and have an engaged list, you may grow your sender reputation to 30. Then you can be a bit more brave and more confidently send emails with more promotional language from time to time. 

On the other hand, if you send an email with a spammy subject line and keep stale subscribers on the list, your email will be more likely to land in the spam filter, have low engagement, and your sender reputation might shrink to 17. Landing in the inbox will take even more effort to overcome the 3 points required.  

 

Design and copy factors

Text as live text

Emails with live text, HTML buttons, and images with accurate descriptive alt text will have a positive influence on deliverability. Because these emails are designed to be more accessible, and load quicker, inboxes reward brands that make their emails user friendly. As a rule of thumb,  if you have at least 35% of your email as text,  your email will have a higher chance of landing in the inbox.

Text to Image Ratio Email Example

This email design has 59% text as live text vs 41% images or text in a graphic, so it will have high deliverability. 

 

Spammy words

In the subject line, content copy and headings, spammy words and phrases will hurt deliverability. 

In subject lines, the following factors will hurt deliverability (this is not a complete list): 

Using spammy words in email copy is also bad, particularly in buttons and headings. 

While not directly spam factors, subject lines that don’t reflect the content of the email inside and mislead users to click (click-bait) are deceptive, can frustrate users, and lead to spam complaints which will, in turn, hurt deliverability.

 

Users’ response factors

How users respond to and interact with your email will influence your sender reputation and the deliverability of future emails. Whether they open, click or ignore your emails, or report them as spam will all have a significant influence on deliverability. 

Opening and clicking – If users open or click your emails, especially if they regularly do it, will have a positive influence on your sender reputation. To increase open and click rates, monitor the type of content that users do and do not like and send more of the content that they engage with regularly. 

Low engagement – Low engagement is most commonly caused by an ageing list or stale content, if users don’t engage, either because they don’t use that inbox anymore, or it’s just busy, or they have switched off your emails, then it’s time to remove them. 

Spam reporting – If a percentage of users report an email as spam, it will affect how your email is delivered to other users too. As few as 0.25% of users (1 in 400) marking an email as spam can have a significant negative effect on your sender reputation, and cause you to land in spam filters in the future. To avoid this, don’t buy lists of email addresses, and make it easier to unsubscribe than to report as spam. 

Unsubscribe – Importantly, users unsubscribing from your emails do not have a negative impact on deliverability, as long as senders respect it. If you keep sending to unsubscribed users, then it will have a very large impact. Make it easy to unsubscribe, so that users don’t report the email as spam instead, and make sure you respect unsubscribe requests. And don’t be afraid of users unsubscribing. If a user unsubscribes, it’s a disinterested user leaving your list. This is much better than them staying on, dragging down your open rates or making spam complaints. 

 

Send quality emails regularly

There’s a balance between sending frequently enough and not annoying your customers. If you send too infrequently, customers will forget that they signed up and gave you permission to email them, which can have a heightened risk of being marked as spam. On the other hand, sending emails too frequently that is lower quality content can lead to customers becoming disengaged. Send emails at least once a fortnight, but not so frequently that the quality of your emails diminishes, up to 4 emails a week if the quality and engagement remains strong. 

 

Email deliverability checklist

  1. Never buy lists of email addresses. If you do this, many users will mark your email as spam.  This can be difficult, and sometimes impossible, to recover from. 
  2. Use a reputable sending service. Established email platforms like MailChimp, Klaviyo and Omnisend put in measures that  ensure brands that use them don’t send spammy emails. They ban companies that send spam. They build sender reputations across all of their clients. 
  3. Remove disengaged subscribers. If users aren’t engaging with your emails, the inboxes will interpret that to mean they aren’t interested. If a user hasn’t opened your emails in 9 months, remove them. 
  4. Follow design best practices. As a rule of thumb, have a ratio of at least 35% live text to 65% images, but 40% or more if you can.
  5. Don’t use spammy subject lines. Spammy subject lines may help pump up a sale in the short run, but will hurt your sender reputation in the long run. 
  6. Monitor user engagement. For example, in Klaviyo reports, view the “Advanced Reports” tab on an email to see a breakdown of open rates by email domain. 

 

As part of our managed services offering, we help our clients stay ahead of any deliverability issues by ensuring every email follows best practice.

 

By Shaun Ernst