You can spend hours (and hours and more hours) crafting the perfect copy, designing a beautiful email, and testing it to ensure it looks great across all possible mobile, web and desktop email clients. But if that email never makes it to the recipient’s inbox, you’ve wasted a lot of time.

Understanding deliverability is critical for anyone involved in email marketing, whether you’re writing the copy or simply signing off on the final email before it is sent. Your overall email strategy and the decisions you make along the way about content, list management and send frequency all impact deliverability.

Here is a quick primer to help you reach the inbox instead of landing in a junk folder.

“Delivery rate” is not deliverability

Most email service providers (ESPs) report how many emails were “delivered” for each message sent, often accompanied by a delivery rate. But those delivery metrics can be a bit deceptive if you don’t understand how they are tracked.

Emails are most often marked delivered by virtue of the fact that no bounce message is received by the sending ESP. When an email bounces, most but not all recipient email services (or mailbox providers) send a bounce message or code back to the ESP. That bounce code could indicate that the mailbox no longer exists, the mailbox is full or the message has been rejected for some other reason.

But what if a message bounces and the recipient server doesn’t return a bounce code? This happens more than you think!

And what happens to the emails that don’t bounce? Well, that depends.

Some of them will make it to the inbox, but others may end up stuck in a corporate-level spam filter or in the spam/junk folder of the email service. In some cases, emails are routed to the spam/junk folder by user-defined rules. And for Gmail users, the email may end up in the promotions tab instead of the primary tab. The promotions tab is not the junk folder, but it’s not the inbox either.

You can see how that so-called “delivery rate” that is reported can be artificially high. This is why we typically refer to the percentage of messages for which we have not received a bounce message the non-bounce rate, because that is really what is being reported.

Factors that affect deliverability

Deliverability is complex, and there are a lot of factors that go into whether or not your email lands in the inbox. Ultimately, it comes down to your sender reputation, also called a sender score, as determined by internet service providers (ISPs). ISPs don’t openly share their specific filtering criteria, but following some basic best practices for both technical setup and email strategy can help ensure a positive sender score and good deliverability for your emails.

Here are a few of the factors that impact deliverability:

• Technical details like your SPF and DKIM settings that help prove to ISPs that your emails are legitimate.
• IP reputation, meaning the sending reputation of the IP your ESP is using to send emails on your behalf, can help or hinder deliverability.
• Message content, especially subject line and calls to action, that can help maintain consistent open and click rates to boost engagement.
• User engagement with your email, including opens and clicks on the positive side, and unsubscribes and spam complaints on the negative side. Your email frequency can impact engagement, so keep that in mind as well. If you’re sending too frequently, your open rates will suffer.
• List management practices to maintain good list hygiene and limit the number of emails sent to unengaged or invalid subscribers.
• Bounce rates, both hard and soft bounces, which tie into list hygiene.
• Spam complaints and spam traps that indicate to the ISPs that recipients are not interested in receiving your email.

Basically, if an ISP sees that you have a high bounce rate, a high complaint rate and a low engagement rate, they may take that as an indication that you’re sending unwanted emails and will thus lower your sender score. Or, if they see that you have low engagement over time, they may filter more of your emails to the junk folder instead of the inbox.

A quick note about subject lines. We often get asked if there are specific words that should be avoided in subject lines to avoid landing in the junk folder. While your content can impact deliverability, the words in your subject line are just one piece of the overall deliverability puzzle. So don’t shy away from using words like “free” or “sale” in your subject line if it makes sense to do so and your overall sender reputation is solid.

How do I know if my deliverability is poor?

If you’re regularly monitoring your email metrics (and we hope you are), there are some warning signs that can indicate problems with deliverability. If you see an increase in complaint rates or a sudden dip in engagement, such as reduced open or click rates, it’s time to keep a careful eye on your deliverability.

Most ESPs offer an inbox placement report of some kind. That report may be included in your contract or it might be an additional fee, but if you’re concerned about your deliverability, it’s important to run an inbox placement report. That report uses seed lists at various email platforms to monitor what’s happening to your email at those platforms.

An inbox placement report should tell you what percentage of your emails makes it to the inbox versus being filtered as junk or spam. The report should also isolate which email platforms are filtering your email, which gives you a clear place to start resolving the deliverability issues.

Recovering from poor deliverability

We recommend regular monitoring of key email metrics to ensure that any small deliverability issues are identified and addressed before they become major issues. Unfortunately, if your deliverability suffers, and especially if your sending domain is blacklisted, it’s a complex and time-consuming process to recover.

If your deliverability suffers for a particular email service, you can take specific action to improve deliverability with that provider. That might include identifying inactives from that email provider and excluding them from your sends while also checking with the provider to see if a block is in place and following their process to remove the block.

If you’ve been blacklisted by one or more email providers, it’s important for you or your agency partner to work closely with your ESP (the platform through which you send your emails) to identify the issues and take strategic action over time to improve your ability to reach the inbox. ESPs that have good relationships with email providers can often assist you with getting a block lifted more quickly. Once the blocks have been lifted, you’ll want to follow best practices moving forward to ensure a good sender reputation and good deliverability.

Need help getting to the inbox? Our email experts are here to help! Drop us a line at or call 314-918-8088, ext. 1.