Email Deliverability Guide: Delivery, Clicks, and Opens


For 2021, Webbula is launching a series of blog posts about email marketing metrics. We have a variety of esteemed authors from the email industry lined up to participate. 

Previous articles you may have missed: 

  • Understanding and Leveraging the Power of Open and Click Reach Rates in Email Marketing by Jeanne Jennings. View that here.
  • Email as a Conversion Tool: 5 Metrics You Should Be Tracking by Tejas Pitkar. Read now.
  • Inactive Email Subscribers: Measure and Minimize Instead of Reactivating by Loren McDonald. Read it here. 
  • Click-to-Open Rates: The Best Measurement of Email Engagement by Betsy Grondy. Read it. 
  • 6 Ways Customer lifetime Value Can Drive Email Marketing Strategy by Emma Warrillow and Tammi Miller. Read it. 
  • The Surprising Link Between Major League Baseball and Email Marketing Metrics by Chris Marriott. Read it Now

  • Email Metrics to Replace Open Rates After the iOS 15 Update by Dela Quist. Read it. 
  • Open Rates Aren't Perfect: How to really know if your emails are engaging by Emily McGuire. Read it now. 

If you missed the discussion watch it here! 


Email metrics are confusing. Maybe not to you but definitely to the manager who claims a 100% open rate should be standard. I get it, your emails rock, so everyone on your email list receiving emails should be happy to open them. 

The reality, however, is different. And the recent development with Apple iOS 15’s update, the one where they hide email opens, dusts off an age-old question: How to properly measure the success of your email campaign?

A lot of email marketers still use the open rate as one of their main KPIs. This in itself isn’t a strange thought: If people open your email, they see your message. It is, however, a pretty flawed metric - especially for email marketing success. 

The thing is, even though the open rate doesn’t do its job as a KPI, it does help you understand the journey of your emails. Let’s dive into that with this Email Deliverability Guide.

A little step back… What is this Apple update about?

Apple’s Mail Privacy Protection, the name of the iOS 15 update, is a blow to those who still use ‘opens’ as a key marketing metric. The update involves hiding the actual open, by loading images in the background. Often, opens are measured through an open pixel that sends feedback to the sending system once the image is opened. 

Though there are other ways to measure opens, a lot of marketing systems depend on this method. The problem is, it’s intercepted pretty easily. 

Preload all images, as Apple does, and your open metric is meaningless. That celebration because you hit 100% open rate is now a deception. But, here’s the fun part - it does mean your emails hit someone’s inbox. 

The Apple update is the extra push a lot of marketers needed, but without it, the open metric would still be a flawed metric. So, even if you only send emails to Outlook users, read on. 

Which strategy is best for improving email deliverability? Download our Pre-Send Email Checklist to find out. 

Why opens are a flawed metric

Some use stronger words like ‘vanity’ metric, but the essence is that the era of measuring opens for email marketing success is coming to an end. Next to the fact that inbox providers are going to block them (Apple is just the first of many), there are a few flaws in the way we measure the opens, specifically through the open pixel:

  • Email previews

Email preview messes up your open tracking, and pretty much every desktop email service inbox provides them. The inbox loads an email preview so it’s ready when the user chooses to open it (IMAP). This way, the user can read the email hours later than the open pixel says they opened the email or not at all.

Email previews generate false positives in your database - your prospect didn’t open it, their inbox provider did.

  • Blocked by recipient

Like Adblockers for your web browser, people have options to not load images or block tracking pixels. My desktop Outlook doesn’t preload images - leading to pretty ugly emails sometimes. But most of all, those images contain a tracking pixel that doesn’t load.

Another way people block tracking pixels is via browser extensions or apps that block everything that looks like a tracking pixel. 

When the recipient blocks images and thus tracking pixels, they could open an email 100 times, but you won’t see it.

  • Forwarded emails

Because the way you measure opens is often based on a unique ID of some sort, every recipient gets its own tracking pixel. This pixel is the same every time someone forwards that email. Though Gmail has a protocol to only show one open, many inbox providers will just register multiple opens from various devices. That can be pretty confusing.

There are other issues that can arise by using the tracking pixel, but I think these are good enough reasons to reconsider relying on your open metric.

What can you learn from opens?

To understand why opens matter, we must look at two other factors as well, email delivery rate and click rate.  Chronologically, these are the rate before the open and the rate after the open. You cannot open an email that has not been delivered and you can’t click an email without opening it. 

Both aren’t the best way to measure email marketing success either. Keith Karlick, guest on this Opens Are Dead video:

“Clicks are a good indicator [of engagement], but you don’t know what they’re going to do next. [You should] focus on on-site engagement.”

We’re not here to be pessimistic about all these metrics, though. Maybe they’re not the best for email marketing success, but opens and clicks are terrific metrics for deliverability

How does that work?

Landing your emails in the actual inbox is paramount to deliverability. There’s just no better way of getting your emails in front of your audience. Every email landing in spam or not hitting the mailbox at all (due to anti-spam measures like blocklisting, hard bounces, or else) is a missed opportunity to engage with your customer. 

Email engagement is, of course, what pretty much every email marketer wishes to achieve. And every inbox provider, too.

So even if you cannot measure what percentage of your recipients open the email,  the metric can tell you a lot about deliverability.

Measure engagement chronologically

Though your open metric is incomplete or provides a false positive, you can use it to get an idea of inbox placement. The open doesn’t necessarily mean someone read it, but it does tell the email sender it hit someone’s mailbox. 

It also means the email didn’t hard or soft bounce, which is a good thing for deliverability. Not every email sending system handles bounces well enough. So, with the open as a “did-not-bounce”-metric, you now have two metrics to know how many email addresses on your list are true - enabling you to practice better list hygiene and avoid spam complaints as well as the spam folder.

When we’re talking about clicks, they help you decide what email addresses should be removed from your list; so-called sun-setting policies. Clicks can be bots as well, but no clicks = no clicks. 

Chronologically, you should take the delivery (or: accepted) rate, opens, and clicks to decide whether or not someone is engaged with your emails and if they can be removed from your list. The after-mail engagement is way more suited for marketing follow-ups. 

Wrap up

I’ve talked quite a lot about opens, but I think the Apple development is a logical consequence of something I read earlier: “We don’t have the right to measure what’s happening in an email anyway” - let alone base marketing decisions on that. And I know there are a lot of cases where opens and clicks are still very, very important metrics, but if they aren’t as important to your business as your marketing team thought, consider seeing them as a deliverability measurement tool instead.


Meet the Author


Tom Blijleven, Marketer at Flowmailer

Verify, Protect and Grow Your Database