Spam Tester, Monitoring and Tracking: How To Measure Your Email Deliverability?

Vladislav Podolyako
Apr 15, 2021
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No matter how advanced your spam testing tool or any other app is, it won’t be of any use if you don’t know the criteria for measuring email deliverability. You must understand how your tools work and what they research to evaluate your inbox.

Don’t you worry: This post will guide you through the methodology of email deliverability audit, educating you on the most important aspects of your outreach. 

What will you learn about?

With this post, you’ll learn the following:  

  • What aspects your email deliverability includes. 
  • How to email spam testers work. 
  • What kind of email audit tools you need. 

Ready to build up your knowledge? Let’s roll!

Spam testing tool or something more: What is explored in mailbox audit. 

Whenever we say, “run a deliverability test,” we mean running full-scale research of your domain and your mailboxes to pinpoint the main issues and find the solution. However, what does this research include?

Inbox placement rate

Your inbox placement rate (IPR) is a metric that tracks how many of your emails land in inboxes instead of spam folders. If you aim for really good deliverability, you must pay attention to your IPR and learn how to read it. 

Let’s say, you launched an email campaign. You use a tool to monitor your results, and it shows you that while AOL receiving servers greenlight your messages, Gmail keeps redirecting your emails to spam folders, creating around 20% of non-delivered emails. 

So what?” you might think. “Around 80% of my emails arrive at inboxes, so that’s a good start.

No, it isn’t. In fact, it’s the beginning of an end unless you take action.

Spam filters and internet service providers have no prejudices or biases. They ground their decisions in the data they receive upon studying your domain reputation. If one service finds a fault within your settings and refuses to let your emails pass, it’s not a nuisance. It’s a problem that would weigh down on your Sender Score and ruin your relationship with the given service. Moreover, it will also affect your relationship with SpamAssassin and Barracuda because they will document your activity with Gmail. 

Thus, monitoring your inbox placement rate allows you to locate such issues before they make your reputation crash and burn. 

The perfect Inbox Placement Rate means that all receiving services let your emails land in recipients’ inboxes. So instead of this report: 

You should see something like this:

When checking your inbox placement rate with Folderly tool, you will also get additional insights and find out which of the following factors might be affecting your results: 

  • Domain record errors.  If you have a poorly generated SPF record or you haven’t added a DMARC policy, receiving servers may reject your incoming messages. In order to fix that, you should review your domain records and make sure they’re up-to-date. 
  • Signature issues. Sometimes, adding links or mailing addresses to the signature can lead to a deliverability drop. Therefore, if you see your IPR going down, try making your email signature more lightweight. Remove any links or addresses it may have, see if the logo icon you’re using complies with the format and weight guidelines. 
  • Click/open tracking issues. There is a downside to using a program for tracking opens or clicks. Even though it’s harmless, email services take extra time to scan and research all the emails with a pixel before letting them into the inbox. When they can’t run a full check, they label such emails as suspicious and ban them from passing through. Due to this, disable your open/click tracking whenever your IPR goes down — this software is the usual suspect. 
  • Spam trigger words. Services like Gmail have an AI-based algorithm that constantly updates its lists of spam trigger words, taking into account phrases and words marked as spam by users. So, the body text in your emails may seem passable to AOL and Yahoo! inboxes but won’t be accepted by Gmail inboxes. Running some A/B testing for different services will help you fix that problem. 

Folderly spam tester provides such information in great detail, letting you skip the investigation and go straight to solving your inbox placement issues.

Domain reputation 

Domain reputation has an impact on lots of things. Will your emails be opened or ignored? Will your bounce rate grow or go down? Will your response rate increase? 

Your domain reputation is your dossier — and email services research it whenever they come across your email campaigns. They take your every action as a sender into account, comparing negative and positive activities, studying the number of complaints and bounces — and then they come up with a verdict. 

They are particularly attentive to the way your messages perform in your recipients’ inboxes. If there is a low Open Rate, no interactions or responses, your domain reputation goes down. If your emails are redirected to spam by users, your domain reputation plummets.

It sounds simple, but in fact, service providers evaluate your domain via intricate algorithms and examine your relationships with every receiver. That’s why it’s not enough to achieve good deliverability with just one email service. All of your intended recipients should contribute to building your good domain reputation.

To secure a positive domain reputation, we suggest you do the following: 

  • Warm-up your domain and mailbox before launching a campaign.  Internet service providers analyze the number of clicks, opens, and other interactions with your emails. This is why it would be wise for you to start by sending small batches of emails that glean high-quality interactions from recipients. 
  • Keep your sending schedule consistent. Stability is not the coin spammers trade with. So the best way to prove that you’re not one of them is to stick to a steady schedule. Send the same volume of emails at the same time every day — and your domain reputation will start climbing up. 
  • Run regular checks. There are many programs and services that give you an approximate outline of your domain reputation. Folderly has an email spam testing tool and a deliverability checker that measure your relationship with your recipients’ mailboxes and give the most accurate evaluation of your status.

In general, domain reputation is a highly complicated thing that can go down during your new email campaigns and get restored gradually, as you show good sender behavior and manage to stay in good graces with internet service providers.

Bounce rate

One of the most important parts of the email deliverability audit is tracking how many emails bounce. A bounced message signifies that an email provider rejected the email you tried sending.

There are 2 types of bounce messages: Soft bounce & hard bounce.

Soft bounces typically indicate temporary delivery issues, such as the recipient’s mailbox being full or a server connection timeout.

Hard bounces indicate permanent delivery issues due to non-existent email addresses or spam issues related to your IP or domain name.

The occasional hard bounce due to mistyping the email address and missing a letter is forgivable.

However, if email service providers notice that your emails hard bounce at a high rate, they could start classifying all your messages as spam since sending bulk messages to unverified addresses is classic behavior among spammers.

Be sure to validate your emails to avoid hard bounces using an email validation service such as NeverBounce or ZeroBounce.

Email authentication practices

Another thing that is measured during a mailbox audit is your ability to prove and exert your authority as a sender. In other words, you must ensure healthy and functional authentication practices. We’ve spoken a lot about these practices, and we will keep speaking about them in the future. Just not to repeat ourselves, we’ll outline these components briefly and give you the essence.

Every modern email spam testing tool runs an audit of these three components, checking whether DKIM is correct and making sure that your SPF record contains all the domains used in your outreach. For example, Folderly provides an in-depth look into the state of your main domain records and outlines the way of fixing errors, if any.

Delivery rate 

This metric is often confused with email deliverability, but in fact, it’s merely one of its components. In short, the delivery rate shows how many emails reached your recipients’ inboxes without getting rejected, bounced, or directed to spam. Due to this, a healthy delivery rate doesn’t mean healthy deliverability.

Nevertheless, it allows you to evaluate the quality of your seed list. For example, if your delivery rate is below 95%, your lists need extra validation and data enrichment. 

You can figure out your delivery rate in two ways. 

Traditional. If you track your sent emails and keep an eye on your bounce rate (as you’re supposed to), you can use this formula.

Digital. Modern deliverability testing tools do their best to break your deliverability down to its most essential components, thus giving you a clear view of your delivery rates. For example, Folderly’s deliverability test provides you with in-depth information about your emails’ journey, showing you the amount that makes it to your prospects’ inboxes. 


Keeping track of perpetrators is a practice that ensures the safety of good, law-abiding people. This practice also works for domains and email services. Any IP addresses and domains that display suspicious behavior, violate too many guidelines, or generate user complaints end up on these lists. It keeps other senders and receiving services alert, letting them know when to automatically block or delete an incoming email. 

However, at the same time, all senders must constantly check blacklists in order to make sure their domain or IP address isn’t featured there. 

Why can you end up blacklisted? It’s hard to give a definite answer because there are a plethora of blacklists, and each of them focuses on a particular aspect of your domain reputation. 

  • Sudden spikes in sending volume. Spammers send a huge number of emails. They aren’t afraid of getting banned — they know it’s inevitable. Therefore, they try to push their message to as many users as possible before their account is deleted. If you suddenly expand your seed list with +100 new emails, some blacklists will consider this behavior suspicious and label your domain as spammy. 
  • Low-quality seed lists. Not checking where your contact data comes from can cost you a lot in the long run. Even if you have a list of hand-curated emails, you need to clean it from time to time because email addresses can expire, get deleted, or changed. People come and go, so make sure not to send an email to an inactive inbox. Spammers pay no attention to such intricacies — they only wish to spread spam. 
  • Increased spam complaints. When recipients aren’t satisfied with your incoming messages or think that you’re uncooperative, they issue spam complaints. Not only do you give your brand a bad name, but also you give blacklists a good reason to mark you as a spam sender. They address all complaints created by recipients and take instant action. 

Folderly scans all main blacklists, including Barracuda and SpamAssassin, and instantly notifies you if it finds your domain name there. Also, it provides you with tips on removing your domain name from blacklists and keeping your reputation safe. 

Vladislav Podolyako
Vladislav Podolyako
Founder & CEO
Vlad’s decades of entrepreneurial wisdom and business building experience have allowed him to successfully mentor a diverse group of business owners, entrepreneurs in growing their companies. A recognized expert in the areas of transforming organizational culture and leadership development, B2B Sales, Marketing, spent more than 10 years building technology products, with a background in communication networks and electronic device engineering.

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