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Tackling Email Bounce Back to Improve Deliverability

Tackling Email Bounce Back to Improve Deliverability: Your Beginner Guide

by | Sep 5, 2023 | Blog, Email Marketing

Imagine you’ve been onboarded onto a company as an email marketing specialist.

The head of marketing explains that they haven’t been running successful email marketing campaigns and they require you to identify the cause of the problem and find a solution.

Once you gain access to their email analytics, you immediately identify the problem. The reason why their email campaigns are performing so poorly is because they have a high email bounce rate.

At the end of the quarter, you explain to your boss and your stakeholders how you were able to tackle the bounce back issue and double the return on investment of your email campaigns.

You can’t help but feel a deep sense of accomplishment and pride at how impressed they are with the progress you made in such a short period of time.

It can be extremely challenging to reap the benefits of your marketing efforts if your emails are not delivered to your customers in the first place.

So, how do you handle such a situation like a pro?

You just need to implement the strategies we discuss here and you never have to worry about this happening to you again. In addition, we will explore:

    • A hypothetical scenario that breaks down the concept of email bounce back 
    • The two types of bounce backs and the reasons why they occur
    • A comprehensive list of preventative measures that you can take to curb bounce back

Let’s jump into the definition of email bounce back and the impact it can have on your brand.

1 – Understanding Email Bounce Backs

Email bounce back, also known as a bounced email or a bounce message, refers to a situation where an email fails to be delivered to the intended recipient and is returned to the sender. 

When an email bounces back, it indicates that there was a problem or failure in delivering the message.

As you can imagine, a high email bounce back is a nightmare for marketers because it damages the sender’s reputation, increases the likelihood of being blacklisted, and provides a negative customer experience.

But, how severe are the consequences?

Well, let’s consider a hypothetical scenario involving a fictional brand called “Juice Electronics” and its email marketing campaign. 

Juice Electronics’ digital marketer, Fred, regularly sends promotional emails to their customer base to announce new product releases, exclusive offers, and updates. 

However, one day when Fred went to check on his brand’s email deliverability, he noticed an issue with their email list: a significant number of bounce backs were occurring.

Fred knew this was not ideal, and he had to immediately identify the root of the problem before his brand faced the following challenges:

  • Negative customer experience: When customers signed up to receive emails from Juice Electronics, they expected to receive relevant and timely information.
    However, if their email addresses are invalid or non-existent, they will repeatedly receive bounce back notifications instead of the intended emails.
    This can lead to frustration and a negative perception of the brand, with customers regarding the brand as disorganized or unprofessional, impacting their trust and loyalty.
  • Brand perception and credibility: If customers repeatedly encounter email delivery issues, it may lead them to question Juice Electronics’ competence, reliability, or attention to detail.
    This negative perception can extend beyond email interactions and potentially impact the brand’s overall reputation in the market. Just look at what happened to Dell when they didn’t listen to and address their customers’ concerns.
  • Decreased engagement and conversions: Bounce backs prevent the delivery of important marketing messages to customers who genuinely want to receive them.
    As a result, Juice Electronics misses out on opportunities to engage with its audience, showcase new products, and drive conversions.
    Without the ability to reach customers effectively, the brand’s marketing efforts are significantly hindered, resulting in reduced sales and revenue.

To mitigate the impact of email bounce backs on his brand, Fred implemented effective email list hygiene practices, such as regularly verifying and updating email addresses, removing invalid or non-responsive contacts, and monitoring email bounce rates.

These practices helped Juice Electronics’ domain maintain a positive sender reputation, increase deliverability, and enhance customer experience. 

Additionally, adopting best practices for email marketing, such as permission-based marketing and providing valuable content, helped rebuild trust and engagement with their target audience.

Definition: Email sender reputation refers to the credibility score given by Internet Service Providers (ISPs) to entities that send emails, determining their email deliverability rates.

2 – Types of Bounce Backs

screenshot of a mail delivery subsystem


“Know thy enemy and in a hundred battles, you will never be defeated.”

Sun Tzu

As we have established, email bounce back is the biggest enemy of your email marketing efforts. 

So, in order to prepare to win any future battles with email deliverability, you must understand the two types of bounce backs:

Hard Bounce

A hard bounce refers to a permanent failure of an email message to be delivered to the recipient’s email address. 

Hard bounces can have a significant impact on your brand’s reputation and deliverability because they suggest outdated or incorrect email lists, potential spamming practices, or poor list hygiene. 

Persistent hard bounces can lead to blacklisting, decreased engagement, and lower deliverability rates.

There are several reasons why a hard bounce can occur, including:

  • Invalid email address: The email address may contain typographical errors, such as missing or misplaced characters, or an incorrect domain name. For example, a customer may accidentally write their email address as “”.
  • Non-existent email address: The email address may have been deactivated or deleted by the recipient, making it no longer valid. Usually, this issue comes back with a bounce message labeled “UNKNOWN_USER.”
  • Blocked email address: Think of email service providers (ESPs) as gatekeepers who run every domain trying to send emails to their users through a filter.
    If your sender’s address is not up to par with their standards, they may suspend your domain or blacklist you, preventing successful email delivery.
  • Blocked by spam filters: The email may be flagged as spam by the recipient’s email server or spam filters, leading to a hard bounce.
    Spam filters are designed to identify and filter out unsolicited or unwanted emails that exhibit certain characteristics commonly associated with spam such as a broadcasted email with a purely financial motive.

The table below outlines common causes of hard bounce (discussed above) and ways to solve them.

Hard Bounce Cause Remedies
Invalid email address
  • Verify your email lists regularly
  • Use email validation tools to ensure the email addresses in your list are correct and in the proper format
Non-existent email address
  • Regularly update your email lists
  • Remove any email addresses that return a “UNKNOWN_USER” bounce message
Blocked email address
  • Check if your domain or sender’s address has been blacklisted
  • Make sure your email content and sending practices comply with ISPs’ standards and policies
Blocked by spam filters
  • Ensure your email content doesn’t exhibit characteristics commonly associated with spam
  • Use spam checker tools before sending your emails

To maintain a healthy sender reputation and improve email deliverability, it is important to regularly clean and update email lists, remove invalid addresses, and take appropriate actions to address hard bounces.

A small list that wants exactly what you’re offering is better than a bigger list that isn’t committed.

— Ramsay Leimenstoll

Soft Bounce

A soft bounce refers to a temporary failure of an email message to be delivered to the recipient’s email address. 

Unlike a hard bounce, which indicates a permanent failure, a soft bounce suggests that the delivery issue may be temporary and that subsequent delivery attempts may be successful.

Some common reasons why a soft bounce may occur include:

  • Mailbox is full: The recipient’s email inbox is at maximum capacity, and no further messages can be accepted until it is cleared out.
    If you keep getting this as the reason for the bounce back, we recommend removing the email address from your list as it might mean that the customer abandoned it and the emails kept piling up.
  • Temporary server issue: The recipient’s email server may be experiencing temporary technical difficulties or undergoing maintenance, preventing the email from being delivered.
    This type of issue usually returns a bounce message labeled MAILBOX_MISCONFIGURATION, which means the recipient is not receiving any mail at the time.
  • Message size exceeded: When a soft bounce occurs due to the message size exceeding the recipient’s email server’s limits, it means that the total size of the email, including any attachments, is larger than what the server can accept.
    Email servers typically impose limits on the maximum message size to ensure efficient email processing and storage.
    For example, Gmail’s maximum limit is 25 MB, which means you can have more than one attachment as long as they all add up to less than the limit.

By addressing soft bounces promptly and taking appropriate measures, you can maintain a healthy email deliverability rate, increase email engagement, and ensure successful email communication.

Bonus Idea: Use analytics to identify patterns in email bounces and optimize your marketing efforts for better email communication and customer reach.

3 – Step-By-Step Guide for Preventing Email Bounce Backs

Now that you understand the enemy, you’re better equipped to take the necessary measures needed in order to overcome email bounce back. 

We have compiled a comprehensive step-by-step guide plush with resources that you can use to overcome email bounce back. Let’s get straight into it:

  1. Build a quality email list: It goes without saying that it’s optimal to only have people who want to be on your email list on it.
    Use organic methods such as offering a lead magnet to acquire email addresses from interested individuals who willingly provide their contact information to ingest more of your content.
    Moreover, to maintain a high-quality email list, implement a double opt-in process where subscribers confirm their email addresses to ensure accuracy and engagement.
  2. Monitor and maintain a healthy sender reputation: Each ESP tracks your domain or IP address to determine your sender reputation and uses a unique algorithm to assign a reputation score.
    It’s crucial that you check your sender reputation regularly using reputable email deliverability monitoring tools such as Sender Score to provide you with insights into your reputation score, email success rate, and other metrics.
    Take necessary steps to improve your sender reputation if it’s low, such as addressing high email bounce rates, reducing spam complaints, and maintaining a consistent sending history.
  3. Optimize email content for engagement: Next, you want to make content that is so valuable and educational that your customers will keep opening and engaging with it, ultimately boosting your sender reputation.
    For example, by crafting compelling subject lines and preview text using design thinking principles, you can improve email open rates and entice recipients to engage with your emails.
  4. Regularly clean and maintain your email list: Keep your list squeaky clean by removing invalid or inactive email addresses every three months to maintain list hygiene and reduce bounce rates.
    Use email verification services or tools such as ZeroBounce to validate and verify email addresses.
    Implement re-engagement campaigns for subscribers who haven’t interacted with your emails for a long time. This helps identify inactive addresses and allows recipients to opt-out if they are no longer interested.

Below is a table summarizing measures you can employ to increase your email deliverability.

Measure Description Benefit
Use double opt-in Ask subscribers to confirm their subscription This can help to ensure that the email address is valid and the recipient wants to receive your emails
Avoid like behavior Use authentic subject lines and avoid trigger words that might be flagged as spam Protects sender reputation and reduces bounce rate
Email validation service Use an email validation service to verify the email addresses on your list before sending out emails Helps remove non-existent or invalid addresses, maintaining list quality
Regular list cleaning Regularly remove hard bounces, unsubscribes, and inactive users from your list to maintain its quality Improves deliverability and maintains list quality
Test your emails Use A/B testing to find what works best for your audience in terms of content, design, and send times Boosts open rates and improves user engagement
Provide easy unsubscribe option Make it easy for recipients to unsubscribe from your list when they want to Prevents spam reports and respects user preferences

If you incorporate the following practices into your email marketing strategy, you will maintain a high sender reputation and increase your email deliverability. 

However, one of the primary reasons why you should strive to maintain a low bounce rate is to prevent ISPs or anti-spam organizations from blacklisting your domain and IP address.

Being blacklisted can have severe consequences on your email deliverability, as your emails may be blocked by multiple ISPs, leading to widespread delivery failures. 

Removing your IP or domain from blacklists is a time-consuming and challenging process that causes significant disruption to your email marketing efforts.

A bad email reputation is like a hangover: hard to get rid of and it makes everything else hurt.

— Christ Marriott

Expert Tip: Analyzing bounce backs can help you identify issues and optimize your email communication to improve engagement and open rates. Use analytics to track patterns and trends.

Reverse the Bounce and Conquering Email Marketing

Well, there you have it. It’s incredible what you can achieve by educating yourself about the best way to handle seemingly complicated subjects.

As we have discussed, tackling email bounce back may seem like a daunting task, but it’s actually quite simple once you understand what it is, the two types of bounce backs, and effective preventive measures.

At OnlineDigitalMarketing, we provide an evidence-based, tactical education system in place that breaks down digital marketing concepts into easily digestible and actionable chunks that you can use to enhance your career as a digital marketer and an entrepreneur. 

Our methods have been taught across 212 countries, to 54 companies, and in four undergraduate universities, resulting in $350 million in revenue generated for our clients.

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Jake Cook


I'm a forever curious entrepreneur that works across ecommerce, analytics, and AI. I've been creating and teaching courses on ecommerce, design thinking, and data science at Montana State University and University of Montana since 2007. Most recently, I've been lecturing and assisting with research and case study development for Harvard Business School.


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