What Is Email Deliverability? 11 Tips & Best Practices Guide (2023)

Ammar Mazhar
Ammar Mazhar

Last updated on

November 14, 2022

On average, 306.4 billion emails are sent every year. Out of all emails, 50% of these emails go into the recipient's spam folder. That is, 50% of recipients never get the email as intended. For email marketers, inbox placement is extremely important. Successful email placement means a high email deliverability rate, while unsuccessful email placement can mean a low email deliverability rate.

Maintaining a good deliverability rate is crucial because it can save the sender from being blacklisted as a spammer by the internet service provider (ISP). Apart from that, a good email deliverability rate helps keep conversion rates high. Also, low email deliverability rates are detrimental to marketing and sales efforts

What can you do to keep your emails from ending up in the dreaded spam folder as an email marketer? What are the industry best practices that you can use to keep your email deliverability rate high? This guide will answer all of your questions.

Are you struggling to maintain your email deliverability rate? With Mailmunch you don’t have to! Keep a check on how your emails are doing in terms of placement, bounce rate, open-rate, and click-through rates and make your email marketing campaigns a success!

What is email deliverability? 

Email deliverability is the ability of an email to arrive in the recipient's inbox. Also, email deliverability is measured as the number of emails accepted by the internet service provider (ISP). 

But it is not as simple as that. Before an email reaches a recipient, it must go through checkpoints such as content filters, spam filters, etc. These filters are set up by the various Email Service Providers (ESPs).

When an email passes through these filters, it lands in the promotional, social, primary, or spam folder. These checks are known as email reputation checks.

Email delivery vs. email deliverability

Email delivery means that the email has been successfully delivered to the receiving server. On the other hand, email deliverability means that the email has successfully reached the recipient’s inbox. It is possible to have a good email delivery but poor email deliverability but not the other way around. That is because when an email reaches the receiving server it is only allowed by ESP to reach the inbox if the sender has a high sender reputation score. If not, then the email is not allowed to reach the recipient's inbox.

Why does email deliverability matter?

The fluctuations in the email deliverability rate will determine where your email campaigns will end up. Failure to reach customers’ inboxes can reduce the performance of a marketing email. Therefore, all businesses need to keep track of this important metric for two common reasons:

1. Helps in conversions

A promotional email is sent to induce the customer to open it. If 40 subscribers out of your 2000 don’t get the email, it is still a 98% deliverability rate. But the open rate might hover just above 20-40%. It means that your message is in your recipients' spam folders.

Hence, keeping track of email deliverability can help you get a holistic view of your email campaigns, like what kind of emails reach your audience more than others or if your email has anything spam triggering. You can increase your conversion rates by keeping your email deliverability rates high.

2. Avoid becoming a spammer

You can avoid being marked as a spammer with high deliverability rates with a spam detecting filters set up by the various ESPs. Adhere to the industry best practices to ensure that your mass email sending doesn’t get you marked as a spammer.

What is a good email deliverability rate?

The average email deliverability rate in the world is 80%. An email deliverability rate upwards of 95% is considered a good email deliverability rate. Reaching a 100% deliverability rate is ideal. 

Still, it is unrealistic because many factors, some of which are in our control and some not, affect email deliverability. The recipient's inbox is full and technical problems like authentication issues can cause your emails to bounce and increase bounce rates.

What is an email bounce?

An email bounces when it fails to reach the recipient’s inbox, social tab, or spam folder, and the recipient never has a chance to see it. There are two types of email bounce: soft and hard bounce.

1. Soft bounce

A soft bounce is a temporary issue in the delivery of an email. Soft bounce can occur due to a full recipient inbox, a down server, or too large an email file. During the early days of email marketing, soft bounces were a problem when inboxes could only allow a limited number of messages. Nowadays, this occurs due to a sudden increase in email sending volume.

Mail servers and ISPs watch inboxes for major spikes in sending volume to ascertain whether the account is used to send spam messages or not. For example, if two emails were sent a week to your subscribers, and now you send two emails per day, you have increased your send volume by 14 times. Therefore, you will see an increase in your bounce rate.

Soft bounce example

2. Hard bounce

A hard bounce is a permanent bounce, meaning that there is something wrong with the email address you are trying to reach. More often than not, it is due to an email address that doesn’t exist anymore. So, when an email address bounces, you should remove it from the list as soon as possible. By keeping your email lists clean, the email bounce rate can decrease.

But, if you don't remove dormant emails and continue to get hard bounces, it will signal to your ISP that you are not keeping your list clean, thereby hurting your email sender reputation and email deliverability rates.

Hard bounce example
Need to keep tabs on the bounce rate? Mailmunch’s Marketing Analytics feature can help you keep track of your emails and tell you how and why your emails bounced.

Factors affecting email deliverability

The factors that primarily affect email deliverability are email sender reputation and email authentication. Also, the content you send in your email and to whom you send it is essential for email deliverability.

Factor affecting email deliverability

1. Email sender reputation

Email sender reputation is a score assigned to each active organization that sends emails by an ISP. The score is calculated through an algorithm that considers many factors such as domain reputation and IP reputation.

As the competition for the inbox increases with each passing day, ESPs are tightening the criterion for a successful email placement. One out of six emails never reaches subscribers' inboxes—only those emails sent by senders having a high email sender reputation reach the subscribers’ inbox. 

1.1) Domain reputation

Domain reputation is critical in determining the email sender's reputation score. ISPs look at various factors such as engagement, bounce rate, spam complaints, and spam traps to determine the reputation of a domain. 

Domain reputation is like credit scores. The better your credit score, the better your email placement will be. Likewise, a negative domain reputation can relegate your emails to the spam folder, and mail service providers can block you.

Rehabilitation of domain reputation can take up to a few weeks to a few months, depending on the negative metrics such as spam trap hits, spam complaints, hard bounces, and low engagement rates. Moreover, you can switch to a new domain, but you also have to fix your business practices to improve your domain’s reputation.

1.2) IP reputation

IP reputation is another essential parameter to consider when determining email sender reputation. An IP address is assigned to each and everything that is connected to the internet. Therefore, websites that don’t have a history of any malicious activity or have connections with domains involved in sending malware have a good reputation, while those with such records have a bad reputation.

IP reputation is critical for email marketing and businesses in general. An IP address with a positive reputation is considered a trustworthy source of information. Suppose you are a business owner, and any one of your servers is hijacked and used to spread malicious content. In that case, the IP reputation will consequently suffer, and so will email deliverability.

2. Email authentication

Email authentication tells ISPs whether or not an email sent is genuine. SPFM and DKIM are the two email authentication protocols widely used. 

2.1) SPF authentication

Sender Policy Framework (SPF) authentication is an email authentication protocol designed to authenticate all incoming emails from different mail servers. Email checks against several IP addresses are authorized to send from that domain server when an email is sent. If you have the IP address, then SPF specifies the receiving server. SPF is used to detect forgery and prevent spam and SPF flattening helps minimize the DNS lookups which is one of the factors that improves email deliverability.

With SPF authentication in place, it is impossible to forge an email because the mail server will reject any email coming from an unauthorized IP address.

SPF authentication process

2.2) DKIM authentication

DomainKeys Identified Mail (DKIM) uses encryption keys and digital signatures to validate the authenticity of emails. The primary function of DKIM is detecting and preventing phishing and email spoofing. Moreover, DKIM appears within the email, unlike SPF, and prevents the receiver from replying to malicious emails. Both SPF and DKIM work closely to avoid spamming and forgery.

The domain owner publishes a cryptographic key. It is a TXT formatted record in the domain’s DNS records. When a mail server sends a message, the server generates and attaches a unique DKIM signature to the email message header. The signature is generated in a unique textual string called a “hash value” encrypted with a private key. The sender has only access to this key.

When the receiver's mail server receives the message, it runs a DNS query to search for the sender’s public key.

DKIM authentication process

2.3) DMARC authentication

When internet service providers restrict IP addresses and domain servers, DMARC comes into play and allows your email to go through using your SPF and DKIM records and assures the receiver's ESP that no malicious activities are associated with this email. Not a necessary authentication to have like SPF and DKIM, but it is a good-to-have authentication to improve email deliverability. 

2.4) Custom domain

Using shared domains to send emails can hurt email sender’s reputation and, subsequently, email deliverability. Also, adding tracking links can get emails flagged for spam. Therefore, the original domain gets replaced by the new one using a custom domain, thus increasing the email deliverability rate.

2.5) TLS encryption

Transport Layer Security (TLS) is an encryption protocol used for encrypting emails while they are in “transit” from one secure email server to another. TLS uses Public Key Infrastructure (PKI) to encrypt messages. Therefore, making it extremely hard for hackers to intercept and read your messages. 

With a combination of symmetric cryptography and asymmetric cryptography, TLS protects your messages from being intercepted. 

With symmetric cryptography, data gets encrypted using a shared secret key between the sender and the recipient. This key is usually 128 or 256 bits in length. The encrypted key then needs to be shared securely. At this point, asymmetric encryption comes into play. 

Asymmetric encryption uses a pair of keys, one public and the other private. The public key is mathematically linked to the private key. This allows the recipient's public key to be used by the sender to encrypt the data they wish to send. But that data can only be decrypted with the recipient's private key.

TLS works with digital certificates, giving users an extra layer of protection. This method verifies that the senders and the receivers are those who they claim to be.

3. Mail server infrastructure

Despite innovations in cloud computing, all the sent emails still depend on hardware and software. Therefore, a robust mail server infrastructure is necessary to have a high email deliverability rate. Having such a mail server infrastructure is costly.

4. Open rate

A low open rate can also play a role in decreasing email deliverability. When an email remains unopened for a long time, it can affect your sender's reputation and, consequently, your email deliverability. 

A reasonable open rate is 20%, but your sender's reputation will be minutely affected if it falls between 15% to 19%. To remedy this, you can check whether your emails are being placed in the primary inbox or the spam folder. Also, check whether the content has issues or not.

If the open rate falls below 15%, you will start seeing a lot of serious email deliverability issues. You can check for spam folder placements and email copy issues to determine the cause. Also, you should check whether or not your email list has inactive subscribers that need to be cleaned.

Open rates below 10% can become a big problem and can also lead to blacklisting as well. This usually happens when senders send spam emails or use purchased email lists. If you are not doing either of these things, you can check the content you sent or update your email lists.

Reasons emails end up in spam folder

Emails sent to the spam folder are technically delivered but can adversely affect your sender's reputation. There are two ways your emails land in the spam folder:

1. Spam trap

Spam traps are email addresses that ISPs own with the intent of catching senders who add emails to their lists without recipient consent. Adding a spam trap to your email list can hurt your reputation and deliverability rate.

There are two types of spam traps: pristine and recycled. 

1.1) Pristine spam trap

Pristine spam traps are emails that are not valid and cannot opt-in to an email list. They are usually available on public websites but are hidden deep into the code of these websites. Pristine spam traps aim to identify email marketers who don’t adhere to best email marketing practices, such as buying email lists.

1.2) Recycled spam trap

Recycled spam traps are repurposed email addresses that are used to detect spammers. Recycled spam traps can be on email list if your email list is more than one year old, you don’t email frequently, or there are invalid or typo emails.

2. Spam complaints

Email programs provide the users the choice to report emails as spam. Spam complaints give users control over what kind of emails they want to see in their inbox. But it takes more than one user reporting to flag emails as spam! 

So, if you keep sending high-quality content that your subscribers require, you will keep your deliverability rate high. Moreover, you should never rent/purchase email lists or send content other than what your subscribers sign up for.

Avoid being blacklisted

High bounce rate, low engagement rates, low-quality content, and a low sending volume are some of the reasons that can land you on a blacklist. Therefore, you must keep your sending volume to moderate levels and ensure a low bounce rate.

Moreover, keep sending high-quality and relevant content to subscribers who have opted-in to receive it.

11 Best practices for managing low email deliverability rates

After you determine the cause of the low email deliverability rate, you can use the following tips to manage low email deliverability rates.

1. Test email deliverability

Keeping an eye on your email deliverability rate is important as it can indicate how your emails are placed in your subscribers' inboxes. Also, if you are facing issues with your email deliverability, you need to test your sender's reputation to see where the problem lies.

Use the best email deliverability software and tools to test your sender's reputation. Moreover, you can also change the email copy and see how it affects email deliverability.

2. Test sender reputation

If you see a drop in your email deliverability, it indicates your depleting sender’s reputation. Therefore, you can do the following things to test your sender reputation.

2.1) Warmup email account

You don’t need to send a huge sequence of emails to test your sender's reputation. By sending a high number of emails, especially from a new email address, the ISPs can target your email as a spammer and, therefore, block your email forever. 

So, the trick here is to start slowly and gradually. Make your email copies personalized so that they start conversations between you and your subscribers. Keep sending emails slowly and increase the number of emails each day or you can use any of the warm up tools.

Keeping your email account warmed up allows you to keep sender scores high and account ready for high-volume email marketing campaigns.

2.2) Maintain a sending quota

After authentication, you are allowed to send bulk emails. But this is not advisable. You should keep track of the number of emails you send daily.

If you start sending emails to a long list of recipients every day, you will get blocked by some of them. Your email service provider will then begin to keep an eye on your activities and can also block your email address temporarily or permanently. 

Therefore, you must keep your emails within a specified quota and make sure that you never exceed the specified quota.

2.3) Be aware of email blacklists

Make sure that you stay clear of email blacklists. They are IP addresses and domains that are suspected of sending spam. Therefore, use an email blacklist checking tool to check your IP address and domain. 

If your IP address or domain is blacklisted, you need to warm your account and make a fresh start.

2.4) Verify email lists

Before you finalize your email lists, you should verify that all the addresses on the list are genuine.

Verified email lists can decrease the bounce rate and increase your sender's reputation score. Also, checking the email lists for typos can reduce the chance of a hard bounce. Therefore, you should clear your email lists quarterly and clean out all the invalid emails before starting a new campaign.

2.5) Have a feedback loop

Email service providers can redirect unsubscribes to a short survey or forms asking them to provide feedback on why they choose to unsubscribe. It is a highly effective method of keeping in touch with users’ needs.

According to research, the response rate of email surveys is approximately 24.8%. Therefore, it is a good practice to allow your email service provider to ask for feedback from unsubscribes. It can help in email deliverability by keeping email lists clean.

3. Send engaging content

The content of your emails is the most critical factor in deciding whether the recipient will open your email or report it as spam, therefore, affecting email deliverability.

3.1) Subject line

The first thing that recipients notice is the subject line. 69% of recipients report emails as spam based on the subject line. Algorithmic spam filters do the same. They search for spam trigger words and, if they find any, place your emails in the recipient's spam folder.

ESPs keep updating these spam trigger words. Therefore, email senders should update themselves regarding which words to avoid in their subject lines.

So, creating personalized and new subject lines that are free from any spam trigger words is the way to go for increased email deliverability. 

3.2) Personalization

People like to be addressed personally. In fact, emails with personalized content have a 29% higher chance of being opened by the recipient. Also, increased open rates increase email deliverability.

Due to cart abandonment, the revenue of $4 trillion is lost each year. But we can recapture 65% of abandoned carts within 60 minutes of them being abandoned with a timely and personalized email

And with a good sender reputation, your email deliverability rate will remain high, thereby helping recapture maximum abandoned carts.

3.3) Text formatting and colors

If your emails' subject lines are in capital letters, this will trigger spam tracking algorithms to relegate your emails to the spam folder. 

Therefore, it is necessary to make sure the formatting of your email content is correct so that it doesn’t adversely affect your email deliverability.

The use of colors is important. As visual creatures, humans tend to look for vibrant and eye-catching things. Therefore, make use of a consistent color scheme in your emails. Don’t use colors that obscure the CTA buttons or render the email unreadable. Recipients don’t like overcolored emails and report them as spam, thus, affecting email deliverability.

3.4) Links

Links are needed in an email for conversion purposes. But adding too many links can land your email in the spam folder. 

Also, email tracking links are mostly blacklisted by ESPs. So, if you add them, they can adversely affect your email deliverability.

4. Mind the text to HTML ratio

Visual content is the best piece of content when it comes to conversions. Emails with visuals in them produce 650 times more engagement than compared to plain text ones. But they can hurt your email deliverability as well. 

Too much HTML content in your emails can trigger a spam response. But if you only send text emails, you won’t be likely to get the conversions you expect. You need to balance the HTML and the textual content of your emails. Experts suggest that a 60:40 text to HTML ratio is the most suitable balance between the two.

5. Provide unsubscribe options

Giving your subscribers a clear unsubscribe option can improve your email deliverability rate. It is better to have an active email list than a dormant one. When you provide a clear unsubscribe option to your subscribers, the email lists will become cleaner when dormant subscribers will unsubscribe, thus, increasing your deliverability rate.

6. Mind sending limits & volume

Consistency is key. A consistent dispatch of emails from the sender can keep the email deliverability rate high and grow your email list. But there are times when businesses have to send an array of emails for marketing purposes. 

But ESPs see many emails as spam, affecting the senders' email deliverability. There is no set limit for how many emails you should send, but you can slowly increase the number of emails leading up to the event.

Let’s say that you send two emails per week to your email list. But an extensive promotional campaign is coming, and you want to increase the number of emails you send to eight. You can send teaser emails about the upcoming event in such a case. The mail servers will have adjusted to the higher sending volume when the event comes.

7. Remove the deadweight

Subscribers that don’t show any engagement whatsoever with any of the emails you send are seriously detrimental to your email deliverability. They are the cause of high unopen rates and bounce rates. So, it is essential to remove such deadweight from your email lists and make your email deliverability rate rise.

In the case of a hard bounce, you should immediately take the subscriber off the email list. But in the case of low engagement rates or open rates, make re-engagement efforts before removing them.

8. Get recipient consent

You don’t want to pop into people's inboxes without getting their consent; you might end up in the spam folder. Also, don’t buy or rent a list or use someone else’s email list. This is one of the quickest ways to decrease your deliverability rate and get blacklisted.

Although there are many places where you can get legitimate email addresses, they still won’t be your legit subscribers. You have to provide an opt-in option to them for that to happen. There are two types of opt-ins: 

8.1) Single opt-in

Single opt-in option needs a visitor to take a single action to become a subscriber to the email list. You can immediately add all the leads to your list with a single opt-in and immediately start delivering the content. 

But with a single opt-in option, you are at risk of gaining fake email addresses that can significantly hurt your email deliverability rate. 

This is one way to go about increasing your email lists. But sometimes, the subscribers don’t know for what they are providing their email address. This is where double opt-in comes in handy.

8.2) Double opt-in

Double opt-in requires the prospect to take two actions before becoming a subscriber. The prospect first fills out a form and then confirms their subscription through a link known as a confirmation email.

In short, any method through which you receive an email address and confirm consent to add it is what double opt-in is.

With a double opt-in option, the leads generated are usually of high quality. Also, your campaigns can get high open rates through a double opt-in option. Moreover, no mistyped or fake emails added to your email list. 

9. Avoid purchased email lists

Avoid sending your emails to an email list that is either purchased, rented, or procured in some other way. It might be convenient just to buy an email list and use it, but it is illegal to send emails without the recipient’s consent in some countries. 

Also, such out for sale lists usually contain spam traps. In short, it is better to avoid purchased email lists altogether.

10. Segment email lists

You don’t want to send your emails to someone who isn’t interested in receiving them. Let’s say that you send an email to two different subscribers - a seasoned marketer and a cook. If your emails are relevant to the marketer, the cook will not be interested in them. He might not even open it or report it as spam. 

This can happen when you don’t segment your email lists. Determining which email goes to whom can keep your sender reputation score elevated and, consequently, keep your email deliverability rate high.

11. Mobile-friendly emails

Organic mobile search traffic in the USA is 63%. So, if your emails and websites are not mobile-friendly, you are at risk of losing both engagement and traffic. Moreover, mobile-friendly emails enjoy a click-rate and click-through rate of 30% and 15%.

Stick to a single column display. Make sure that you keep the font size to 13 or 14 points, minimum. Moreover, keep your important content and call to action buttons easy to find for your subscribers. So, make your emails responsive for multiple mobiles and enjoy a high deliverability rate. Ensure that you avoid using hyperlinks and avoid cluttering hyperlinks.


Email deliverability is an important parameter to consider when starting an email campaign. Factors such as authenticity, mail server infrastructure, and open rates majorly affect sender reputation and email deliverability rates. By staying away from purchased email lists, making your emails mobile-friendly, and sending high-quality content, you can keep your email deliverability rates high. 

Moreover, provide clear unsubscribe options, remove inactive subscribers, and mind sending limits and volumes for better deliverability. 

So, if you are looking for a complete email deliverability guide and digital marketing tool kit, then look no further than Mailmunch! Choose from 1,000+ email templates, 100 landing pages, and pop-ups, and get creative with your email marketing campaigns! Keep a lookout on the metrices using our Marketing Analytics feature!

Frequently asked questions

1. What is a good open rate for emails?

A good email open rate should be between 17-28%. But these numbers can vary depending upon the industry you are working in. 

2. What is sender reputation?

An email sender reputation is a score that an internet service provider (ISP) provides to an organization that sends emails. The higher your sender reputation score, the more likely ISP will deliver your emails to the intended recipient.

3. What is a spam trap?

Spam traps are email addresses used by ISP to identify senders who don’t follow email best practices.

Author Bio

Ammar Mazhar

A voracious reader and a music lover, Ammar has been writing engaging and informative content for over 2 years for B2B and B2C markets. With a knack for writing SEO-optimized content, Ammar makes sure that the results speak for themselves.


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