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Email Deliverability: What is it and How to Measure it

My Post - 2020-02-26T131620.339.pngThere are numerous ways to optimize your email marketing campaigns. None of them’s more critical than building high deliverability.

Only after you’ve successfully reached your recipient’s inbox can you encourage them to take action. Whether you want them to download your ebook, book an appointment, or buy one of your products, your message won’t help you achieve that if it’s stuck in the spam folder.

If you already know this much – great! In that case, you don’t need more convincing. ☺

In this post, we’ll tackle two important topics: what is email deliverability and how to measure it.

And if you’d like to learn about improving your inbox placement and email campaign profitability, consider reading this article:

Email Marketing Best Practices

Bonus: Optimize your email campaigns with this Email deliverability Checklist and this comprehensive Email Deliverability A to Z Guide


What is email deliverability

Also known as inbox placement, the deliverability rate tells you how many messages reach your recipient’s inbox – or one of their folders/tabs (other than the dreaded spam folder).

You can calculate your email deliverability using the following formula:

[(# of emails delivered to the inbox/tabs/folders (excl. spam folder))/(# of sent emails – # of emails that generated a bounce)] * 100%

Looks complicated? Let’s look at an example.

Let’s say you’ve sent out an email campaign to 100 recipients. Out of those messages:

  • 60 ended up in the recipient’s inbox
  • 30 landed in the promotions tab
  • 5 landed in the spam folder
  • 5 generated a bounce

In this case, you’d say your deliverability rate is 95%!

Here are the exact numbers we’ve used to arrive at this number:

[(60 + 30)/(100 – 5)] * 100% = 95%

Before we go any further, we’d like to make a small note first:

There’s a whole argument of whether inbox placement is the right term to use when referring to deliverability since we’re also counting other tabs and folders in the equation.

We think that the promotions tab (and other similar ones) was developed to help email recipients manage and consume content they’ve subscribed to more efficiently.

Although some marketers try to get their emails out of the promotions tab, given the latest developments from Google (leader in the market), we suggest that you think twice before you follow that path.

We believe that happy recipients make happy customers. And Google has some pretty cool plans for the promotions tab.

Problems with measuring email deliverability

The theory looks simple, but measuring email deliverability isn’t an easy task.

When you look into your email analytics dashboard, you’re usually missing one key element from the equation – the number of emails that ended up in your recipient’s spam folder.

Why is that crucial piece of information missing? That’s because email servers your messages are sent to don’t return this information. They may inform you about the fact that the email address you’re trying to reach is inactive, or its mailbox is full, but not what happened after the message was received.

Here’s the exact response you or your email service provider would receive regardless if your message was placed in the inbox or the junk folder:

smtp;250 Ok

As you can see, there’s no information as to how the message got filtered, i.e., whether it landed in the primary inbox, the promotions tab, or the spam folder.

This is because how your emails get filtered within your recipient’s mailbox depends on various factors – including how they interacted with your previous communication.

In other words, if your message ends up in the subscriber’s X spam folder, it doesn’t mean it won’t show up in the primary tab for user Y or any other user, for that matter.

So, if it’s not possible to know when your emails end up in the spam folder, how on earth do email deliverability tools work?

Three kinds of email deliverability tools

There are three kinds of deliverability tools, and we’ll talk about them individually.

1. Email spam checkers

Alright, the first set of tools we’re going to have a look at is called spam checkers.

Sometimes they’re standalone tools; other times, they’re built into your email marketing tool, as is the case with GetResponse.

Spam checkers let you analyze the content of your emails and check them against spam filters. They’re looking at various elements inside your email message like the amount and types of links, images and their size, your coding, what’s inside the headers, etc.

After running a quick test with a spam checker, what you receive is the likelihood of your emails going to spam. It’s usually presented on a scale from 1 to 5, where 5 means your chances to hit the junk folder are the highest.

There are both pros and cons of using these types of tools.

Advantages of using spam checkers:

  • They’re quick – the test usually takes a few seconds
  • They’re easy to use – it’ll take you only one moment to learn how to use one
  • They’re rather powerful – based on hundreds of various tests, powered by industry-recognized programs like SpamAssassin

Disadvantages of using spam checkers:

  • They have limited scope – they only look at the content of your emails, excluding factors like recipient’s behavior or some of the ISPs filters

2. Seed list testing tools

Another way to check your email deliverability is to use seed email lists.

In their simplest form, they’re just a bunch of email addresses that you send your email campaign to, before launching it to your whole database.

These email addresses are usually set up to include different ISPs (like Outlook or Google), devices, and browsers.

After sending your email campaign to a seed email list, you should know whether your email is displayed correctly in all major email clients, whether it lands in the inbox or returns a bounce.

Unfortunately, that’s only theory.

As we mentioned earlier, email deliverability is a bit more complicated than that.

We’ve already told you that when ISPs filter incoming emails, they also like to look at how recipients respond to them.

If you were to create a seed list and send your email campaigns to it and then open it up for testing – what do you think would happen?

You’d be giving signals to the ISP that these messages are important to you.

Because of that, these emails would more likely be placed in your inbox, which wouldn’t necessarily be the case for other recipients of your emails.

Consequently, your results could potentially be biased and give you a false overview of the condition of your email deliverability. – Read more