The last thing any email marketer or other professional who does outreach wants is to see their emails returned when it’s on their way out. Otherwise, it increases their bounce rates.

Whether your campaigns are labeled with messages “rejected,” “bounced,” or “failed,” it all means one thing – they’re not hitting the intended inboxes. What are you doing wrong? This is precisely what this guide is all about: to answer, “Why do emails bounce back and how to lower your bounce rate?”

But before we go through them one by one, let’s first understand the basics of an email bounce.

What is An Email Bounce?

An email bounce happens when an email cannot be delivered to the recipient’s inbox. This happens for various reasons, which we will discuss later.

The destination mail server or the sender email server sends this Non-Delivery Report (NDR), which usually details what caused the email delivery failure. Pro Tip: Keep your bounce-back email as it often includes messages or codes. Read them carefully and understand the reason why your email bounced so that it won’t happen again in the future.

Two types of email bounces

There are two email bounces: a soft bounce (temporary) and a hard bounce (permanent).

  • Soft bounce 

An email soft bounce means that the email address is valid and received by the recipient. However, it still bounces because the message or attachment was too large for the receiver’s inbox, the server may have crashed or is under maintenance, or the mailbox was full.

Furthermore, this bounce is temporary since it can be easily remedied by fixing the server, shortening your campaign or newsletter, or the recipient cleaning out their inbox.

Once the recipient frees up some space, they will automatically be able to receive your newsletters as usual.

  • Hard bounce

On the other hand, a hard bounce occurs when the email is rejected because the email address doesn’t exist or is invalid. This is a permanent type of email bounce and indicates a functionally useless contact. Also, the email address should be deleted from your list.

Soft bounces aren’t that bad, but hard bounces can degrade your email deliverability or do serious damage to your sender’s reputation.

Email bounce rate

The email bounce rate is the percentage of email addresses in an email list that did not receive the message.

Unlike other email marketing metrics, such as opens and clicks, where a high rate means good, a high email bounce rate is bad.

The acceptable email bounce rate depends on the industry. Generally, it shouldn’t be higher than 2%. Anything higher than that requires you to find the cause to reduce the number. Here are some best email marketing practices to help you handle email bounce rate problems.

A few averages for soft and hard email bounce rates across different industries are as follows:

  • Agriculture and Food Services: soft bounce (0.50%), hard bounce (0.32%)
  • Architecture and Construction: soft bounce (1.18%), hard bounce (0.73%)
  • Beauty and Personal Care: soft bounce (0.33%), hard bounce (0.26%)
  • Business and Finance: soft bounce (0.55%), hard bounce (0.43%)
  • Computers and Electronics: soft bounce (0.79%), hard bounce (0.47%)
  • E-Commerce: soft bounce (0.26%), hard bounce (0.19%)

How is Email Bounce Rate Calculated?

Email bounce rate = (# of bounces/ # of delivered emails) x 100

So, let’s say you send a newsletter to your 1,000 subscribers and 10 of those bounce back. Here’s how you compute your bounce rate: (10 / 1,000) x 100 = 0.01 x 100 = 1%

Pretty simple. Right?

Now that you know how the email bounce rate is calculated, let’s look at the 10 common reasons your emails might bounce.

10 Reasons Why Emails Bounce Back

1. Invalid Email Address

One of the common reasons why emails bounce back is because the supposed recipient’s email address is invalid or has already expired. In this case, the service provider is forced to bounce back the emails because of these conditions.

These issues often arise when you use an old email list, buy an email list, or use unverified emails. These also happen when you make typographical mistakes when entering the email address.

More specifically, the email bounce-back code you’ll likely receive when encountering this issue is “550” or “550-5.1.1”. Simply put, the email address does not exist. Hence, there’s no way to deliver the email.

2. Recipient’s Inbox is Full

Another reason email bounces is that the receiver’s inbox is full. Several email apps only provide a defined storage capacity for individual users. For instance, every Google Account is given 15 GB of storage shared across Gmail, Google Photos, and Google Drive.

Outlook offers the same storage capacity as Google, while Yahoo offers up to 1TB storage for its users. Other email service providers may offer free unlimited or large storage capacity, but the maximum number of emails sent or received per day is limited.

Once the defined storage capacity exceeds, the server will no longer allow new emails and alert the mailbox owner that they need to take action to resolve the issue.

3. Blocked by the Recipient

Emails bounce back if the recipient’s mail server blocks your domain or email address.

Moreover, the recipient or server may suspect any malicious activity, decide it’s not trustworthy, no longer wants to hear from you, or have written rules to prevent certain emails from getting through their inbox.

Eventually, it decreases your email deliverability and sender reputation.

However, some servers are stricter, especially government offices, hospitals, and schools. If you experience a problem sending emails to those recipients, you may have to reach out by an alternative means and encourage them to include your email address in their “safe senders” list.

4. Receiving Email Server is Temporarily Unavailable or Overloaded

Your email campaigns can bounce back if they are in the category of “undeliverable.” It may mean the recipient mail server is temporarily unavailable, couldn’t be found, or was overloaded. Additionally, servers go offline for different reasons.

For instance, it’s like sending a traditional letter to a house on an unknown street or doesn’t exist. Typically, when the emails are undeliverable, they deliver soft bounces. So, keep an eye on these email marketing errors if they persist because there may be a more serious issue.

5. Known Spammer

Your recipient’s email service provider may mark emails from your account, depending on your reputation or email history.

Unfortunately, if it shows you have been sending spam emails or someone in your IP range is spamming, your messages can get trapped in the spam filters. For instance, the most common reasons for this kind of email bounce are as follows:

  • One of the domains to which your emails are sent is blacklisted (temporarily).
  • The emails you sent over time to the recipient mail server have constantly appeared as spam. Therefore, the email provider stopped delivering your email to its users.
  • Brand name or reply-to address has a poor reputation
  • One of the IPs to which your campaign is sent is blocked (temporarily).

6. Blacklisted

Your email marketing efforts can go down the drain if your recipient’s email server has blacklisted you. A blacklist is a database of IP addresses believed to send spam.

To get off the blacklist, address the reason for blacklisting. For instance, if your email account was used to distribute spam or got hacked, change your password or activate two-factor authentication to avoid unauthorized use of your email address.

7. DNS Failure

A Domain Name System (DNS) failure occurs when users cannot connect to an IP address through a domain name. If this happens, the email cannot be delivered since there is a problem with the receiver server’s DNS.

This email bounce issue may or may not be temporary. However, the common sources of DNS failure are issues in the router or modem, computer, ISP (Internet Service Provider), computer, or browser.

8. Message or Attachment is Too Large

If you pack your email with huge attachments or megabyte-heavy photos, it may cause a soft bounce. Furthermore, this happens because there’s a filter, and it may identify the attachment as a potential virus source.

Additionally, the recipient’s system may not allow certain files or attachments. To resolve this issue, try not to exceed the 10 MB attachment file limit.

9. Natural Database Decay

Email databases decay on their own by 22.5% per year. It could happen because people stop using their old email address, use a new one, or an unqualified lead opts out of emails.

Whatever the reason why your recipient’s email address changes, you should focus on maintaining a healthy list. Remove those no longer interested in your offers or emails and add new leads.

10. Evolving Industry Standards

SPAM filters constantly improve their algorithms to protect recipients from potential threats. These filters can block phishing attacks and viruses and segregate spammy emails from safe ones.

Over time, though, the list of what is considered “spammy” changes. Each year, a Domain-based Message Authentication, Reporting & Conformance (DMARC) conference is conducted to establish the best email practices to protect consumers from dangerous and annoying emails.

While it is a good thing, it requires updates on your part as a marketer to continue landing in your recipient’s inbox.

8 Tips to Reduce Email Bounce Rate

Luckily, email bounces show up quickly after you send your campaign. Such speed makes it easy to spot the problem that needs your attention. We share below some of the tips to reduce your email bounce rate!

1. Use a double opt-in system

Using a double opt-in system will not only reduce your email bounce rate and improve the quality of your contact list. All these can result in better overall email marketing.

What is double opt-in?

Double opt-in is a system of adding a new contact to your mailing list. It involves collecting an email address and sending confirmation emails to the user.

After the confirmation link is clicked, the process is completed, and the email account is added to the email marketing list. As a result, the chance of spam addresses is significantly reduced, protecting your sender’s reputation.

2. Authenticate your email domain (don’t worry, it’s not hard)

SPF, DKIM, and DMARC are three common methods of email authentication. Using these three will reduce bounce rates and improve email deliverability. Yet, email marketing statistics show that less than 40% of brands use these authentication methods.

Authenticating your domain signals the receiving email server that you have permission to send newsletters from this domain and that you are a legitimate sender.

Read Next: SPF, DKIM, and DMARC explained

3. Maintain a clean and healthy email list

Reduce your bounce rate by observing good email hygiene. This task entails removing uninterested and invalid email addresses from your contact list and sending only valuable messages to your subscribers.

Additionally, an alternative to deleting inactive email addresses is to segment your subscriber list. Try moving the inactive subscribers for a while to a segment in which you only send them good discounts and offers.

You could also lessen the number of emails you send to such a list. For example, if you used to send an email once a week, try sending two emails per month to this segmented list. Who knows? The engagement on this segmented list may improve.

4. Don’t send spam (or anything that looks spammy)

Do everything possible so your emails won’t be labeled as spam. Moreover, it is always worth the effort to double-check your message to make sure it doesn’t look spammy.

Sending emails that trigger the spam filters, acting as gatekeepers of sorts in the email world, may eventually cause your digital communication to land in the spam folder.

If you want, you can use a third-party service to test your email for spamminess. Or better yet, avoid using spam triggers to maintain your industry’s ideal email bounce rate.

5. Use clean, simple code

Hide and seek may be a fun game for children, but if you apply that in email marketing, you risk harming your deliverability. This is because an awkward-looking code is off-putting to spam filters, not just to human eyes.

On the contrary, using a clean and simple code ensures that your email renders correctly. As a result, communication gets its point across in a way that subscribers take action.

Double-check these things to ensure your email code stays clean, lowering your bounce rate:

  • Super large font sizes
  • Bad tags, incorrectly nested tags, too many closing tags
  • Embedded Javascript
  • Invalid font face
  • Font color is almost similar to the background color (hides text in the email)
  • Providing attachments
  • Use of iFrame
  • HTML comments in code
  • Not standard ASCII characters

6. Get personal

Everyone wants to feel like the email they received is just for them. That’s why customer engagement ROI is almost guaranteed when a marketer learns a fraction of the information about their target audience.

Not to mention a staggering 293. 6 billion business and consumer emails are sent daily. Also, email marketing is one of the highest-performing ROI marketing channels worldwide. So, why leave the big marketing pie to chance by not personalizing your content and making it relevant to the recipient?

Our recommendation is you divide your list into these groups:

  • Location
  • Company size
  • Industry
  • Function
  • Role

When we say personalization, we don’t just mean the first name and call it a day. Go beyond to show your target audience that you really care.

7. Contact your list consistently (but not too often)

Did you know that one of the things that could hurt your email deliverability is not emailing to your list too often but not emailing them at all?

The two main reasons why you should keep your emails regular and consistent are:

First, you remain in your email subscribers’ minds. That way, they know it’s you emailing them. Not emailing your list consistently increases the chance of your subscribers for forgetting your brand or why they signed up for your contact list in the first place.

Then, they may delete your future emails without giving them a look. And this, my friend, can seriously affect your reputation score and increases your bounce rate even further.

Second, bounces happen in low numbers gradually if you contact your subscribers consistently. This is why it’s in your best interest to spice up your email communication every now and then and diversify your email.

8. Use a trustworthy email marketing tool

Successful execution of email marketing best practices is only possible if you have a trustworthy and reliable email marketing tool in place.

Last year, email marketing automation was one of the hottest trends in the email marketing industry. So, you can hop onto the bandwagon. Or invest in an email marketing tool that allows you to probe your email campaign performance in-depth.

Wrap up

There you have it.

Hopefully, with all the tips and tricks we shared, it won’t take too long to improve your deliverability.

Quick Takeaways:

  • An email bounce happens when an email cannot be delivered to the recipient’s inbox.
  • The email bounce rate is calculated with this formula (# of bounces/ # of delivered emails) x 100.
  • The acceptable email bounce rate depends on the industry but shouldn’t be higher than 2%.
  • A high bounce rate in your email marketing campaign. It could mean you’re not meeting your subscribers’ expectations.
  • High bounce rates often indicate issues with maintaining your email list, permissions, content, and evolving industry standards.
  • Email bounces show up quickly, so you can quickly take action to improve your deliverability.

If you need any help in your email campaign, feel free to book us a live demo, and we’ll be more than glad to guide you.

Happy Emailing!