What Do Your ESP Metrics Really Tell You About Your Deliverability?

What do your ESP metrics really tell you about your deliverability?

Knowing the deliverability of your email campaigns is essential to understand how well it’s doing. It also can be one of the hardest metrics to nail down.

You might think you know your deliverability because you can look at the dashboard in your email service platform and see that 99% of your emails got delivered. That’s your delivery rate – the percentage of emails that were received successfully by an email server or ISP.

However, that’s not the same as your deliverability. Deliverability measures how successfully your email messages reach your subscribers’ inboxes instead of being routed to their spam folders or getting blocked outright by an ISP’s filters. That’s an important difference because, for many subscribers, out of sight means out of mind.

The 2021 Consumer Email Tracker published by the UK’s DMA found 46% of subscribers say they check their spam folders at least daily, and 11% say they check it at least hourly. What we don’t know, however, is how often they can spot valuable messages that should have gone to the inbox instead.

6 campaign metrics to track for deliverability

Deliverability can be hard to pin down because the campaign metrics your email service platform reports after each send most likely don’t address it directly. You can’t assume, for example, that a high delivery rate equals high inbox placement.

Instead, a combination of several key campaign metrics can help you estimate your deliverability and whether it’s improving or declining.

These metrics are all part of your ESP’s campaign reporting. If your ESP doesn’t report these metrics, you probably should look for one that does. In our work with Trendline clients, these metrics are one of the first things we review when tackling deliverability issues.

  1. Open rate

This is the percentage of subscribers who opened an email message. In 2021, the average open rate varies from 18% (Campaign Monitor) to 23% (Mailchimp).

In theory, the higher the open rate, the more likely your email messages are being delivered to the inbox where subscribers will see them. If your open rate is 15% or less, or if it is declining, this can indicate an ongoing deliverability issue as well as a content problem.

We say “in theory” because the open rate is not a reliable engagement or campaign success measure – and it’s about to become even less reliable. Here’s why:

  • It’s often both overcounted and undercounted. An open is counted every time a tracking pixel in an email message pings back to your email server, supposedly when a recipient opens the email.

But spam filters can inflate that count by loading the tracking pixel even without an open or depress the count by blocking the pixel from loading – as when a subscriber blocks images from downloading.

  • Apple Mail will disable pixel tracking. Apple will effectively break the open as an engagement metric once and for all when changes to its Apple Mail service go into effect. The result will be both undercounting from users who opt to block tracking pixels or overcounting because Apple will download images to their servers automatically, counting them as opens even if a subscriber doesn’t open the message.

(Note: Trendline SVP Alex Williams explains what’s happening and how you should get ready for the coming changes in this blog post: Apple’s ‘Mail Privacy Protection’ is an Earthquake for Email Marketers.”)

  1. Click rate

The click rate is the percentage of clicks counted on an email message. The click rate is considered more reliable than the open rate because it assumes that subscribers have already opened and read the email message.

However, spam filters can inflate click counts by clicking on links automatically as they search email content for spam and fraud. Clicks in the first few seconds after delivery likely are from these filters. This is especially true in B2B email. We at Trendline recommend disregarding these early clicks as coming from filters and not people.

  1. Bounce rates

This is the percentage of permanently or temporarily undeliverable email messages per send. If 3% or more of your messages bounce when you send a campaign, you might have problems with the sources of email addresses on your list.

Four problems can push up your bounce rates:

  • Bad addresses: Besides misspelled or malformed addresses, which your email platform should remove immediately, bad addresses can also include fake addresses from bots or users who want something from you (gated content, contest entry, shopping discount) but don’t want your marketing emails.

Real-time address checking and anti-bot protection can keep these addresses out. But you also should review the user experience at opt-in. You might need to do more to explain your brand value and email benefits to persuade customers that your email program is worth a real email address.

  • Rate-limiting: Also called throttling, this happens when an ISP automatically reduces the number of emails it accepts from your server, usually because it thinks your messages might be spam. This can indicate problems with your sender reputation at major services like Microsoft or Yahoo Mail.
  • “Mailbox full” bounces: These normally are temporary bounces – the email address is valid, but the mailbox is full and not accepting more email until the mailbox user either clears out old email or adds capacity.

It was a common problem before webmail services like Gmail and Yahoo began offering seemingly bottomless storage capacity. Today, when you hit a “mailbox full” notice, it means the address has likely been abandoned, and the owner will never open your messages. That hurts your sender reputation and makes you more vulnerable to spam traps built from abandoned email addresses.

  • Spam block: This indicates something in your email message, sending address, or IP set off a spam filter, which then rejected the message. You might not be able to figure out exactly what caused the problem – instead, it’s a signal to investigate further.
  1. Spam complaint rate

A zero complaint rate isn’t always good news. It could mean that your emails aren’t going into the inbox where recipients will see them. Nobody wants a high spam rate, but you should have an occasional one or two as another indicator that people are seeing your messages in the inbox where they belong. Aim for a target rate of less than 1 complaint per 1,000 messages.

Note: Not every ISP offers a feedback loop to report complaints, so your rate might be artificially low. Use ISPs that do have feedback loops, like Yahoo, where your complaint rate should be less than 1 complaint in 1,000.

  1. Delivery time

If you are sending emails from a dedicated IP (you’re not sharing it with other senders), and a particular campaign is spread out over a longer time than usual, this can indicate rate limits or throttling, which in turn can indicate a falling reputation at the receiving provider.  You can see evidence of the same issue on shared IPs or IP pools, but it’s harder to tell if it’s you that’s the problem or one of the other senders on that IP/pool.

  1. Conversion rate

The five metrics we already discussed have one thing in common – they all measure activity on your email. Your conversion rate is different because it reflects the percentage of customers who took an action you wanted beyond your email, like buying or signing up for something. It measures how successfully your email led customers to do what you wanted them to do.

If your other metrics are off, however, that can hold down conversions.

How you define the conversion, and thus figure out the percentage of people who converted, will depend on what you want them to do. Measuring conversions can also depend on the integrations you use in your email program and how accurately they track your customers and report their activity.

Using metrics to diagnose deliverability

You’ll get the most meaning out of these metrics when you track each one over time. A single metric viewed at one point in time – like your click rate – will mean more when you can tell whether it’s rising or falling. With that information you can go back to your acquisition sources or campaigns to look for correlations.

And we’ll repeat another key point: You should see all of these metrics in your email or CRM/ecommerce dashboards. You might need another layer of reporting to uncover your conversion rate if you do use outside platforms, but you still should have access. If you don’t have it, ask for it. Your email success can depend on it!

Author: Zack Aab, Trendline – Before learning how to use email, Zack worked in computer repair, blacksmithing, video production, and knot-tying, but not all at once. Zack has his CIPP/US certification, is definitely not a lizard person, and likes normal human things like email and data privacy and basking on sunny rocks. Follow Zack on LinkedIn