How to Test Your Email Deliverability? A Step-by-Step Guide

With roughly 281 billion emails sent and received each day, our inboxes have never been more crowded. This makes it really hard for email marketers to catch their prospects’ attention. 

However, getting your email opened and replied to might not be the biggest challenge in email marketing.

Before you start wondering why your emails fail to generate any results, make sure they actually reach the intended recipients and check your campaign deliverability.

Helping our customers streamline their cold email outreach every day for the last 5 years, we at Reply know a thing or two about email deliverability. That is why we’ve decided to put together a detailed checklist on how to test and improve it (along with some of the tools we use). So, let’s dive in.

The hands-on guide on how to test and improve your email deliverability

The SPAM folder is where emails go to die. Once you get there, chances are you’ll never fully recover. Even if your recipient finds your email there and moves it to the inbox, there’s no guarantee that your following emails won’t go straight to the SPAM folder again.

That is why it’s so important to make sure your email deliverability is high before sending your campaign.

To do that, you’ll need to check the following aspects of your email campaign:

  • technical setup and authentication
  • the quality of your contact list
  • your email content
  • audience engagement 

Now, let’s take a closer look at each one of those aspects (we’ll also share some expert tips and useful tools to help you test and improve them).

1. Technical setup and infrastructure

Proper technical setup and authentication are some of the most challenging but also the most important elements of a high email deliverability rating.

So, when setting up your email campaign, keep an eye on the following settings:

  • Email authentication

For proper domain authentication, check the following records:

  • Sender Policy Framework (SPF)
  • DomainKeys Identified Mail (DKIM) 
  • Domain-Based Message Authentication, Reporting, & Conformance (DMARC)
  • Pointer (PTR)
  • Mail Exchange (MX) and Address (A).

Pro tip: To manage those records, you’ll need access to your domain settings (GSuite users will also need access to admin console there to generate DKIM). These procedures, however, might differ depending on your domain hosting provider, so check in with them for official instructions.

  • SpamAssassin score

SpamAssassin is an open-source anti-spam platform by Apache. Using various techniques, the platform rates your email based on how it complies with general anti-spam rules. 

Pro tip: The higher your SpamAssassin score the better: any message with a score of -5 or lower is considered SPAM.

  • IP and domain blacklist testing

Lastly, make sure you are not included in any blacklists (especially if you are using a dedicated IP for your email campaigns).

Pro tip: To get yourself off a blacklist, go to their official website and follow the instructions. The removal process might be self-service (which is relatively fast and easy) or time-based (which is automatic but also might take a week or two).

How to test it?

mail-tester screenshot

One of the best and most user-friendly tools we’ve tried is mail-tester.com. All you need to do is send your email template to the email address generated by the service and click “check the score”. 

Once you do that, you’ll get a detailed report on your technical setup, including SpamAssassin score, domain authentication, blacklists, etc. The report will also include useful links to learn more about the existing issues and how to fix them.

Mail-tester spam score, screenshot

In addition to the technical aspects of your email deliverability, mail-tester.com analyzes your email content as well (which we will discuss later).

One downside, however, is that  a free subscription plan offers a limited number of attempts – up to three tests a day. You can get more test attempts starting at €50.

Among other tools that can help you check your domain reputation, we recommend senderscore.org and reputationauthority.org. Both of them are super-easy and free to use.

2. Contact list

The quality of your prospect list also has a direct effect on campaign deliverability. The key metric to keep an eye on here is your bounce rate (i.e. how many emails failed to reach the recipient for some reason such as invalid email address).

Pro tip: while the average bounce rate might vary depending on your industry or even location, try to keep it to a minimum – 5% or lower – to steer clear from SPAM filters.

To make sure the quality of your contacts doesn’t affect your email deliverability, check the following:

  • Double opt-in

The best way to avoid being flagged as SPAM is to send emails only to the contacts who have willingly joined your mailing list (and preferably confirmed their wish twice). This, however, is only applicable in email marketing, not cold outreach.

  • Lists source

If you need to send emails to people who are not your subscribers, as is the case with cold emailing, it’s better to build a list yourself instead of buying one. Purchased lists are typically of poor quality – full of spam traps and outdated information.

  • List hygiene

As mentioned above, it’s crucial to keep your list clean and up to date. Stale lists typically get higher bounce rates which might result in lower deliverability. To avoid this, make sure to verify emails on your list once in a while.

How to test it?

Use tools like Verifalia or Neverbounce to keep your list clean and weed out invalid or potentially dangerous contacts. Both of them allow for bulk email validation and have flexible pricing plans.

Neverbounce screenshot

3. Email content

As mentioned above, email content also impacts deliverability. Email providers have learned to analyze the words you use.

Here are several things about your email content that you should keep in check:

  • SPAM words

Some words or phrases are known to trigger SPAM filters, including “free”, “cheap”, “cost”, or even “success” and, quite ironically, “we hate SPAM”. You can easily find a complete list of those words online, for example, Hubspot has a pretty exhaustive selection, segmented by industry and type.

  • Text-to-image ratio

As email content is relatively easy for SPAM filters to scan, it is a common practice to use images to mask text containing trigger words or hidden links. That is why it’s best if you don’t use images at all or, at least, keep the text/image ratio in your emails reasonable (ideally 80:20 or higher).

Pro tip: For complex emails, even the tracking pixel can cause significant deliverability problems. In this case, it’s better to disable it (although, this won’t let you track your open rate).

  • External links

These are also typically associated with SPAM, so it’s better to keep their number to a minimum. If you still need to include a link, make sure it leads to a reputable website and don’t use URL shorteners.

  • Sentiment

Don’t write in all caps or use too many exclamations – it doesn’t just hurt your deliverability, but also makes you look extremely unprofessional or even rude.

Pro tip: Always try to make your emails short and to the point; neither your recipients nor SPAM filters like longreads.

How to test it?

As mentioned above, mail-tester.com allows you to check your email content along with the technical aspects of your email. Namely, the tool will analyze the HTML elements, alt attributes, text-to-image ratio,  while checking for any short or broken links.

As for SPAM trigger words, you can check it manually or use free tools like emailcopychecker.com.

If you are using Reply for your outreach automation, there’s an AI-based feature that lets you check your email copy for SPAM words as well as other aspects that contribute to its overall quality (i.e. readability, word count, etc.).

Reply's email quality screenshot

4. Audience engagement 

The way that recipients interact with your emails can also be used to let email providers and SPAM filters know whether you can be trusted or not. Namely, the more recipients ignore your emails, the worse your reputation will get. 

The key metrics you should keep an eye on here are your open, click-through, and reply rates

Pro tip:  Obviously, it’s better to have as many opens and responses as possible. If your open and reply rates are lower than 2%, you are at high risk of being blacklisted by anti-spam systems.

How to test it?

Unfortunately, there’s no way to test your audience engagement and find out how many recipients will open and click your emails before you actually send them. 

The only thing you can do to keep your high deliverability high is to keep track of your campaign metrics and regularly remove inactive prospects (the ones who are not interacting with your emails) from your list. 

Before you hit “send”

Testing each of the listed criteria separately, as shown above, can give you a pretty solid understanding of your email deliverability. However, there’s one more way to see how likely are your emails to get into the prospect’s inbox.

Namely, you can see where your emails will land (as well as what they look like for your prospects) by sending them to a seed list of test email addresses.

How to test it?

There are several tools that allow you to conduct seed list testing. For example, we are using Glockapps.

The testing process is pretty straightforward. All you need to do is include a unique tracking ID into your email. Next, you will get a list of test addresses for different email providers (or you can use your own seed list) to send your message to. 

Once you send your email, you can see where they land (i.e. inbox or SPAM folder) for each mail service provider as well as get basic recommendations on how to improve your inbox placement rate for each provider.

You can also test your email deliverability using Mailtrap. This tool makes it really easy to test your emails in a development or staging environment. It allows you to see how your message is rendered by a webmail, analyze your spam score, and get recommendations on how to fix it if any issues were found.

Wrapping up

Since SPAM accounts for 56% of all email traffic, service providers are increasingly looking to protect their users from unwanted messages. As a result, even legit emails might not be immune to ending up in a SPAM folder instead of the recipient’s inbox.

That is why it’s so important to put a solid deliverability testing process in place.

Hopefully, the checklist above can help with this task and make sure your emails won’t fall victim to SPAM filters and safely reach their destination!