As crucial as deliverability is to email marketing, it can also be an enigma. A deep understanding of email deliverability requires a firm grasp of the technologies behind email. Still, many marketers glaze over when you start talking about networks, servers, and IPs.
And that’s okay. Not every marketer needs a deep understanding of the inner workings of deliverability. Marketers need to understand what deliverability is and how well they’re doing.
Let’s start with the easy part.
What is Deliverability?
Deliverability is the percentage of emails accepted by a recipient’s networks. Deliverability is calculated by dividing email deliveries by total sends. On the flip side, emails that aren’t accepted are called bounces. The bounce rate can be calculated by dividing bounces by sends.
It’s important to note that a delivery doesn’t mean the message made it to the recipient’s inbox. Filtered messages are a subset of deliveries. Filtered messages are automatically sorted into areas other than the primary inbox. This includes, but is not limited to, spam and junk folders.
How Well Am I Doing?
Most email systems are pretty good about reporting deliverability at both a campaign and an aggregate level. This makes it pretty easy to see how you did.
Information on past campaigns is essential, but what we’re really after is how we will do. After all, we want to avoid potential deliverability issues and mitigate their impact on our campaigns.
Things get a little trickier here. Our dashboards, unfortunately, don’t come with deliverability predictions (at least not yet).
While deliverability can sometimes trend predictably, it’s also prone to sudden and significant drops. Getting caught on a major blacklist, for example, can cause a massive drop in deliverability overnight.
Although these changes in deliverability may seem random, they are definite indicators of trouble to come. Conveniently, many of these metrics can be found right on your basic email marketing dashboard.
So, what are they?
1. Spam Complaints
Spam complaints stem from recipients who have taken the time to notify their provider of unwanted or unsolicited emails. As you might imagine, spam complaints are a factor in sender reputation.
Due to the obvious connection to deliverability, spam complaints tend to be overvalued in terms of their impact. Spam complaints are important, but they’re only one element of the equation. They shouldn’t be viewed as be-all and end-all.
2. Hard Bounces
Hard bounces are emails that are permanently undeliverable. The most common cause for hard bounces is sending to email addresses that do not exist or have been decommissioned.
Some turnover is expected for email addresses, and accordingly, a certain number of hard bounces are expected. For most industries, a hard bounce rate somewhere around 1% is acceptable. You can find an industry-by-industry breakdown in this report.
Excessive hard bounces are expected for “spray and pray” spammers. Spam filters view them as a sign that you’re not familiar with those you’re sending to. Over time, hard bounces can diminish your reputation and lead to blocks.
3. Soft Bounces
Soft bounces are the counterpart of hard bounces. Soft bounces are emails that are temporarily undeliverable. They can be caused by something benign like a full inbox, a down mail server, or an email message that’s too large. Soft bounces can also be spam-related. Mail servers can block your email if your domain, IP, or sending address is blacklisted. Blocks can also be triggered by issues in your message content, like overly promotional copy, overreliance on images, and poorly constructed code.
Many soft bounces – particularly repeated soft bounces – are viewed by filters as a sign of spam. It’s a good idea to suppress contacts after a certain amount of soft bounces. Many systems will do so automatically based on a user-defined threshold (usually two or three soft bounces).
A total bounce rate of 4% to 5% is average for B2B companies. This puts an acceptable soft bounce rate between 3% and 4%, though it’s best to keep bounces as low as possible.
Soft bounces can also be a good indicator of arising deliverability issues. Pay special attention to spam-related soft bounces. If you see an increase there, it’s a good idea to look over your content for anything triggering filters. After that, run IPs and send domains through a blacklist checker to see if the problem is at the sender level.
4. Engagement Rate
The engagement rate is the percentage of recipients interacting with an email message. It’s calculated by dividing the total number of opens and click-throughs by the number of emails sent.
Engagement rate isn’t the most obvious deliverability metric, though it is important. Spam filters view engagement as a sign of relevance. Messages that are repeatedly delivered and ignored will be directed to “Junk” or “Clutter” folders, which, in turn, will contribute to a negative sender reputation and make it more difficult for these messages to get delivered in the future.
Dips in engagement rate can be one of the first signs of trouble due to the cascade effect on message filtration and sender reputation.
To improve engagement rates, separate long-term inactive contacts from your mailing lists. Repeated sends to these contacts drive down engagement rates. These contacts can always be returned after being reactivated in a targeted re-engagement campaign.
5. Sending Volume
Sending volume is another major factor in deliverability. Spam filters will look for both spikes in traffic and a high overall volume.
Ideally, it would be best to keep sending volume as low as possible while maintaining consistency. Realistically, this isn’t always an option. Focus first on preventing significant jumps in email volume, then work to cut unnecessary sends.
Be aware that spikes in volume can lead to sharp drops in deliverability, whereas a high, sustained volume tends to produce smaller but ongoing drops. Both situations are manageable but can cause problems if left unchecked.
Let us know what you think:
- What email deliverability metrics do you monitor?
- Do you have a dedicated team member or third-party service?
- What tools do you use?
This post was originally written by Matt Leap on March 11th, 2019. It was updated by Acadia Otlowski on February 11, 2020, and Caitlyn Smith on December 16, 2022.