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Email Deliverability Definitive Guide for 2024

23 min read
21478 reads

Imagine spending hours writing compelling copies and offers only to find that your cold emails never reached your prospects. You need to see that creating a perfect email copy and hitting the send button is not enough. Email deliverability is the ingredient to crack success.

Your emails pass through different stages of strict filters before somebody even notices, and without a thorough understanding of email deliverability, all your efforts might go to waste.

But this deliverability guide is here to help. You will know actionable to get your cold emails delivered to the inbox, and you can monitor your outreaches to trace the early signs of low deliverability and fix them on time.

Before we dive into detail, let’s first understand what email deliverability is all about because it’s important to know the process of determining whether your email ends up in the inbox or spam so that you can be better prepared for the following actions.

What is email deliverability?

Deliverability refers to the success of an email in reaching its intended recipient’s inbox without being blocked or flagged as spam by the ESP.

After an email is sent, it goes through the ESP’s spam filters, which have several stages before reaching the recipient. When the spam filters pass your emails, the recipients can see them in their inboxes. Otherwise, there is a high chance you are getting marked as spam or not getting delivered if spam filters feel your emails compromise their set standards. 

Well, there is no defined formula to calculate email deliverability because, unlike email delivery rate, deliverability relies on the ability of your emails to reach the targeted inboxes. You will see the discussion in detail in the later section. 

If your email deliverability is leaky, your cold emails will sink into a sea of unnoticed emails—the primary goal of any cold email campaign is to get noticed. Therefore, discussing how spam filters affect your cold email performance is important.

Why is deliverability important for any email outreach?

Email deliverability plays a significant role in a successful outreach campaign. The goal is to send an email to many recipients and ensure the email is delivered successfully. 

A high email deliverability rate means that your email campaign reaches your intended audience, and you have a better chance of achieving your campaign objectives. On the other hand, if you have prolonged email deliverability issues and ignore them, it may have an irreversible impact on your ability to send cold emails if not addressed early. 

Poor email deliverability can have several negative consequences, including:

  • Damages sender reputation: You can damage your reputation as a sender if your emails are often marked as spam or bounce. As a result, future email campaigns may not be more successful.
  • Blocklisting: ESPs may blacklist your domain or IP address if your emails continuously land in the spam. As a result, you may have trouble getting your emails delivered with the same domain.

On the other hand, the benefits of good email deliverability include:

  • Improved email reputation: You can establish a positive sender reputation by consistently reaching and engaging your target audience’s inbox.
  • Increased daily sending limits: When your email-sending practices are consistently good, your ESP may increase your daily sending limit. Your email campaigns can reach and perform better if you send more daily emails.
  • Increased audience engagement: Getting your emails to recipients’ inboxes increases their chances of opening, reading, and taking action. Your email campaigns will have a higher engagement rate, and the ROI will be higher.

Here’s a comprehensive list of the impact of both poor and good deliverability.

Before we delve deeper into the factors that affect email deliverability, it’s important to understand the difference between email deliverability and delivery rate.

What is the difference between Email Delivery & Email Deliverability?

When people start cold emailing, one of the most prevailing misconceptions is that deliverability and delivery rate are interchangeable. But there is quite a difference; both are important in sending successful emails.

The email delivery rate indicates how many emails got successfully delivered to the recipient’s email server. It does not consider whether the email landed in the recipient’s inbox, spam folder, or bounced back. Emails with a high delivery rate tend to reach their intended recipients’ email servers, regardless of whether they land in spam or inbox.

Email Delivery Rate = (Total Emails Sent – Bounced Emails) / Total Emails Sent x 100.

Meanwhile, deliverability is more than whether the email was delivered. It measures the rate of emails landing in the primary folder or inbox of the recipient.

How does email deliverability work? 

Spam filters play an active role in cold emails to reach their recipients. 

The deliverability of your email depends on various factors and steps that determine whether it reaches your target audience or ends up in their spam folder. When an email is sent, it goes through multiple filters that evaluate its content and reputation. Your emails will be delivered to the recipient’s inbox if they pass these filters. 

Nevertheless, if your email gets flagged as spam, it will not be delivered to the recipient’s inbox, damaging your reputation as a sender. Therefore, ensuring your email meets the standards set by ESPs and passes the various filters is crucial for maximum email deliverability.

To understand how spam filters affect cold email outreach, let’s look at what factors they consider.

What are the key factors affecting email deliverability?

Email deliverability can be affected by several factors laid by spam filters, including:

  1. Sender reputation: ESPs determine whether to deliver your emails based on your email-sending behavior and reputation. A low sender score or spam history can lead you to spam.
  1. Email authentication: The authentication process lets ESPs verify the sender’s identity and prevent spam. Authenticating your emails using SPF, DKIM, and DMARC pre-dominantly affects email deliverability.
  1. Email content: Deliverability can also be affected by the content of your email. Your emails may be marked as spam if you use spam trigger words or phrases. You should provide valuable content to your recipient and use a clear and concise subject line.
  1. Bounce rate: High bounce rates indicate your email list is unhealthy, creating a suspicion that you are opting for spam activities, thus negatively impacting your deliverability.
  2. Complaint rate: Receivers who report your emails as spam or unsubscribe from your list can negatively impact your sender’s reputation.
  3. Engagement rate: ESPs track recipients’ interactions with your emails, including opens and click-throughs. A high engagement rate can positively impact the sender’s reputation and deliverability.
  4. Sending pattern: The ESP tracks the volume and frequency of your emails. Your deliverability can be negatively affected if you send a large number of emails at once.

Additionally, it’s important to know when your deliverability is at risk. Here’s how you can determine when your deliverability is at stake.

How to know if your email deliverability is good or poor?

Monitor these key metrics to determine whether your email deliverability is good or poor:

Delivery rate: It measures the proportion of emails delivered to recipients’ inboxes. It is a good indicator of email deliverability if your delivery rate is consistently high (above 95%). The following section discusses in detail what tools you can use.

Open rate: The percentage of emails opened by recipients is known as the open rate. The open rate of your emails (over 30%) indicates that your subject lines are resonating with your target audience. Conversely, constantly receiving less than 30% open rates is a red alarm to check your deliverability.

Bounce rate: The bounce rate represents the percentage of emails not delivered to the recipient’s inbox. A high bounce rate (above 3%) can indicate that your email list may not be adequately maintained. It can seriously hamper your email deliverability. 

Complaint rate: Complaint rate refers to how many recipients mark your email as spam or unsubscribe from your mailing list. Complaint rates over 0.1 percent can negatively impact your sender’s reputation and deliverability. Feedback loops can tell you how many recipients have complained about you and their reasons.

Fall in engagement: If you see a pattern in the drop in engagement, such as CTR and reply rate, it’s a good idea to investigate your deliverability.

Fall in conversion: Drop-in email deliverability can directly affect your conversions or sales because you would be engaging lesser people to close your deals. Therefore, if there is an occurrence for a while, email deliverability needs to be checked first.

These metrics help you stay on the right track regarding deliverability, but if you can’t measure deliverability or find the reasons, you won’t be able to fix it. So let’s explore the tools you can use to keep track of your deliverability.

What tools can be used to identify low email deliverability?

A low email deliverability rate can be diagnosed using various tools. The following are some of these tools:

Inbox placement tools

A tool for inbox placement allows you to analyze and monitor the performance of your email campaigns. Using these tools, you can learn how many emails land in the inbox and how many are in the spam folder. 

You can improve Inbox placement rates by identifying delivery issues and taking necessary action. Inbox placement tools include:

Google Postmaster (free to use)

Gmail Postmaster is a free tool for monitoring email deliverability. It provides information about your domain’s reputation, spam rate, and authentication.

Gmail classifies senders’ reputations based on their history of sending spam into four categories: Bad, Low, Medium/Fair, and High. 

When a sender sends a lot of spam, their mail will almost always be rejected or marked as spam due to their bad reputation.

You can track your delivery errors, as the graph above shows the percentage of rejected or temporarily failed emails.

It also lists the reasons for email failures, such as rate limit exceeded, suspected spam, spammy content, unsupported attachments, DMARC rejection policy, low IP/domain reputation, and listing in public blocklists. A list of sending IP address records is also provided.

Google Postmaster helps you check the spam rate. Email spam rates are calculated by comparing the percentage of spam marked by users with the percentage of spam sent to the inbox of active users. 

Postmaster is easy to use. Here are the steps:

  • Sign up for a Google Account if you haven’t already
  • Login to Postmaster Tools
  • In the bottom right corner, click “Add”
  • Enter your authentication domain DKIM or SPF (We will discuss authentications in detail in the later part)
  • Continue by clicking “Next”
  • Make sure your domain is verified

MX ToolBox

MX ToolBox manages email deliverability and inbox placement issues by identifying potential problems with delivery. 

Various email deliverability tests are available:

  • SMTP diagnostics
  • Blacklist checking
  • SPF/DKIM/DMARC record verification
inbox placement

There is an easy way to determine which ESP prevents your messages from being delivered. Furthermore, MX Tools will alert you if your authentications have a problem. If your emails aren’t landing in the inbox, they will give these signs, as shown in the image below. 

MX toolbox

Blacklist detection tool

Email blacklist detection tools are software or online services that determine whether any of the major email blacklists has blacklisted a particular IP address or domain. Using these tools, you can learn whether an email server or domain is flagged, why it was blacklisted, and how to remove it from the blacklist. 

You can check whether you are blacklisted with Spamhaus, one of the most popular tools.

Follow these steps to determine if your IP address is on the Spamhaus Block List.

You can check your domain name or IP address at Spamhaus.

You have nothing to worry about if you see a message saying Your IP has no issues. If there are no issues with your IP, a message will display.

However, if it says that your IP address is on the SBL (Spamhaus Blacklist), you can find the possible reasons in the below message and rectify that.


Spam content detection tool

The Mail-tester tool is a free tool that lets you check your email content for potential spam triggers. Your email is scored based on how likely it is to be marked as spam by the tool.

mail-tester test results

Follow these steps to test your email content using Mail-Tester:

  1. First, create a new email in your email client.
  2. Then, to test the email, send it to an email address provided by Mail-Tester.
  3. Mail-Tester will process your email after a few seconds.
  4. Finally, click “Refresh” on the Mail-Tester website.
  5. After analyzing the content, Mail-Tester provides an email score based on various factors, including SPF and DKIM settings, message headers, and content quality.
  6. Based on Mail-Tester’s score and recommendations, you may need to change your email content to improve your deliverability.

Seed testing tool

You can test the deliverability of your email campaigns using a seed testing tool by sending test emails to a set of “seed” addresses. 

A seed address is typically an email account belonging to a trusted third party. If you send test emails to these addresses, you can determine whether they get delivered to the inbox and not the spam folder. 

You can test the deliverability of your emails across multiple email service providers using GlockApps

GlockApps seed testing steps are as follows:

  1. First, log in to your GlockApps account.
  2. At the top of the screen, click the “Email Tests” tab.
  3. Start a new test by clicking the “New Test” button.
  4. Send your email campaign by entering the subject line and sender address.
  5. Please add your seed addresses to the seed list. It can either be entered manually or uploaded from a file.
  6. Select the ESPs and email clients you want to test next.
  7. Launch the test and wait to see the results.
glock apps

In the end, GlockApps will provide you with detailed reports about the delivery and placement of your emails across different email clients and ISPs.

If spam filters are blocking your emails, you can check which ESP is blocking them. You can then use the best practices and the standards of the particular spam filters and fix your problems.

How to improve your email deliverability?

You can improve Email deliverability by following best practices and ensuring your emails reach your targeted inboxes. To improve your email deliverability, follow these steps:

Setup authentication 

Email deliverability relies heavily on authentication. When you authenticate your emails, you build trust with your email service providers (ESPs) and reduce spam complaints. 

Authentication protocols include three main types:

SPF (Sender Policy Framework): SPF is a simple email validation system that detects email spoofing. It allows the domain owner to specify which IP addresses are authorized to send emails on behalf of that domain.

To add SPF, you would need to login into your DNS settings from your hosting provider or domain registrar like GoDaddy, Zoho, etc.

  • Create a new record with the type “TXT.”
  • Name: A record’s name is its hostname or prefix without the domain name. You can enter @ or a prefix, such as mail, to place the record on your root domain.
  • Value: The SPF rule to be applied, such as v=spf1 mx -all (it can be different for different providers), indicates emails are only allowed from your mail server. 
  • TTL: Keep TTL at default settings
  • Save the record

DKIM (DomainKeys Identified Mail): DKIM allows the ESP of an email recipient to verify that the domain owner indeed sent it.

To add DKIM, you need to log into your DNS settings again and follow the instructions:

  • Create a Text “TXT” or “CNAME” record per your hosting provider standards.
  • Paste the value or setting for DKIM (from your hosting provider)
  • Set your Host like in the given example is s1._domainkey where s1 is the DKIM selector, 
  • Click the Save button. 
  • You can check whether your DKIM is published here.

DMARC (Domain-based Message Authentication, Reporting, and Conformance): DMARC is a policy that combines SPF and DKIM to determine the authenticity of an email message.

You can set these records in your DNS settings.

  • You can add a DNS TXT record or modify an existing one by entering it in the TXT record for _dmarc:
  • In the first field of the TXT record, enter
  • In the second field, enter the text for your DMARC record.
  • Depending on your DNS provider, the field names for DNS TXT records may vary for different providers. 

    Example: v=DMARC1; p=none;rua=mailto:[email protected]
  • Make sure you save your changes.

Setup secondary domains

Creating a secondary domain to prevent your primary domain from being burned is helpful. This method allows you to continue sending emails with different domains even if your primary domain suffers reputation issues.

This way, it can save the domain reputation for your original business name, and you can distribute your sending strategy with secondary domains.

You should send less than 50 emails from each email account from a domain per day. You can also use a cluster of secondary domains to send your emails for high deliverability.

Let’s say your business name is, and you can buy secondary domains like,, etc.

Set up custom tracking

Custom tracking domains ensure you send your links or images (if any) through your own domain instead of a shared one to ensure good deliverability. 

Add a CNAME record in your DNS settings with the value your email host gives. For Saleshandy, use and host field trk (or any other name you prefer) to create a custom domain. Here’s how you do it from Saleshandy.

Afterward, you can verify your custom domain records from whatsmydns

Warm up your domains

Before sending a large volume of emails, warm up your domain. Then, gradually increase the volume over a few weeks by sending small segments of your list small quantities of emails. As a result, you will maintain a positive relationship with the ESPs.

Manual warm-up is a highly tedious task. However, you can take help from automated warm-up tools to engage with your inbox humanly.

One such tool is TrulyInbox. You can sign-up and connect your email accounts easily.


Clean up your email list

Your deliverability gets negatively impacted when a hard bounce occurs due to an invalid email address. Keeping your email list clean and removing invalid addresses will reduce hard bounces.

You can use email verification tools to keep your email list clean. For example, Usebouncer is a popular tool for verifying leads in bulk. It’s estimated to give good results. You can sign-up to Usebouncer for 100 email credits for free.

Bouncer email tool

To clear a healthy email list, choosing reliable sources is the best. Building an effective lead list ultimately helps to reduce the bounce rate.

Personalize copy and reduce spamminess 

Content reputation is one of the critical factors spam filters consider when scoring your domain reputation. Therefore, using these best practices, you can create a high-deliverable message that positively impacts your delivered ESPs.

Avoid spam keywords: Avoid using spam trigger words, excessive punctuation, or special characters in your email copy. Instead, keep it clean and simple. Use tools like to ensure your emails don’t land in spam.

You can use tools like Saleshandy’s Writing Assistant, where you can detect spam-triggering words and get an alert with a low score if your copy contains a lot of spam.

Personalized tags: Email personalization is key to high deliverability. Therefore always use merge tags and make your messaging personalized. Make sure to create unique content for all prospects on the list. In addition, it helps boost your reputation.

Manually personalizing your emails can consume much time and hamper your productivity. Thus, automation is a good idea for sending personalized emails at scale.

Like, here, in Saleshandy, you can easily merge tags and spintax to create unique messages. Saleshandy sends them in a human-like pattern to keep you upbeat among different ESPs.

Plain text: Keep your email content free of HTML, as many spam filters measure the text ratio to HTML. Therefore, if you can remove HTML elements from your content, your content can do better in terms of deliverability.

Avoid Links: Links are the most suspicious factors, spam filter judge when you land on their servers. Remember that the cold email’s purpose is to get a reply. You can make better copies and put a valuable CTA asking questions, which helps you depend less on the links. 

Nevertheless, if using a link is essential, ensure you don’t use more than one.

Opt-out links: Always make it easier for prospects to opt out from your cold emails. It gives a positive impression to your ESP that you value and respect your recipients and don’t intend to spam them with a pushy campaign. 

As a best practice, you can set up email preferences. Whenever a recipient clicks the opt-out link, he would see a list of email preferences, for example:

  1. I don’t want to receive any more.
  2. I’m Interested in receiving only essential updates only.
  3. It was a mistake. Please keep me updated. 

Therefore, it helps you increase your engagement chances and decrease your unsubscribe rate.

Test emails: It is safe and good practice to test your emails before sending them to your recipients to see if they are in good shape. Whether your merge tags are working or if it lands in promotions or spam. It can help you fix problems before the spam filter catches them.

Keep track of your contacts

Building an email list is an integral part of cold emailing. As a part of it, you’ll need to place a list policy to stay ahead.

List policy is a strategy for engaging with your active contacts and dormant contacts in the list.

Here are the suggestions you can follow:

  • Don’t purchase email lists. Always build one.
  • Make a relevant list because if your list is irrelevant, it will receive a low engagement rate, triggering low deliverability.
  • You can re-engage with your contact who haven’t replied to you. It increases the chances of engagement rate.
  • Practice removing dormant or inactive leads from your campaigns time-to-time to avoid spam filters making a suspicion.
  • You can set up a Feedback loop, a process that lets you know when it marks you as spam, writes a spam complaint, or user unsubscribes to monitor spam rate and optimize your outreach accordingly.

Read more : 12 Best Email Deliverability Tools For 2024 (Pricing + Features)

How to monitor email deliverability?

Duly monitoring your email deliverability is a recommended practice. It ensures your emails are performing well. Always take a proactive approach and fix the issue beforehand. Keep track of several important metrics and benchmarks.

Here are key metrics to track and industry benchmarks to keep in mind:

Keep an eye on these metrics

a. Drop-in opens: If your email opens drops suddenly, it may indicate that it was marked as spam or was not delivered.

b. Drop in clicks/engagement: A drop in the engagement or CTR may be that your message did not reach your targeted inboxes or your content wasn’t engaging if you see a drop in clicks.

c. Spike in unsubscribe rates: Irrelevant content or sending too many emails can cause a sudden spike in unsubscribes. It is an indicator that your deliverability can be affected.

d. Spike in spam complaint rates:  Your email might have been delivered to a spam folder if you see an increase in spam complaints (you can use the Feedback loop discussed above), or it might have too much promotional content.

e. Spike in bounce rates: When you experience a sudden spike in bounces, you might need to clean up your email list or send emails to invalid addresses. It is the biggest hurdle in getting healthy deliverability.

Read more : Email Deliverability Metrics To Monitor

Industry Benchmarks

For the best deliverability experience, continually optimize your campaigns near to or better than the industry standards. Here you can take an average reference and see if your deliverability falls below the stats.

  • According to ReturnPath, the average inbox placement rate is 85%.
  • The average spam placement rate is 15%.
  • The average spam complaint rate is 0.02%.
  • The average bounce rate is 0.5%.

You can refer to BenchmarkEmails’ stats for industry-specific benchmarks and compare your data to keep track of deliverability.

If you see the drop, counter it duly, putting your domains in the audit with the deliverability tools suggested above and improving your cold emailing experience.

We’d like to hear how this guide helped you with deliverability.


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