Email Bounce Backs: What They Are & How to Fix Them (Guide)

Email Bounce Backs: What They Are & How to Fix Them (Guide)

Ivan Escott
Ivan Escott

Partnerships Manager at Respona

Sending an email successfully might sound like a simple process, but it isn’t always quite that easy.

As well as formatting the email in the right way based on your recipient and the occasion’s formality, you also need to pay attention to factors that’ll affect your email deliverability.

If you don’t take the latter into consideration, there’s the risk of your email bouncing back and never reaching your recipient’s inbox at all.

This is exactly what the following guide is all about; taking a deep look at the reasons why bounced emails happen and what you can do to avoid them.

More specifically, we’re going to cover:

  • What bounce back emails are
  • Why emails bounce back
  • The different types of bounces

Plus, how to reduce high bounce rates and many more tips to optimize your email outreach and email marketing efforts!

If you’re eager to learn more, let’s get started straight away.

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What is Email Bounce Back?

Email bounce back is when an email you send can’t be delivered to your recipient’s mailbox due to a certain issue.

As you’ve probably guessed, this is something that any marketer, link builder, or salesperson would like to avoid.

After all, imagine investing time in finding someone’s email address, creating a high-quality email, personalizing it, but then it never reaches your intended recipient.

That’s not great, right?

A constantly high bounce rate can have a negative impact on your marketing and outreach efforts, as well as your sender reputation; this is a score that internet service providers (ISP) assign to an email sending IP address, which determines how trustworthy it is.

If your sender score is 99/100 like in the following image, then you have less chance that your email will bounce back or end up in spam.

Sendpulse sender score
Image Source: Sendpulse

Actually, many email service providers (ESP) like Gmail and Outlook will penalize a sender’s reputation if the bounce rate is over 5%.

As a general rule of thumb, you should aim for a bounce rate below 3%, but we’ll cover this extensively further on in our guide.

What we recommend you keep in mind is the fact that you need to keep your bounce rates as low as possible by following ethical and so-called “white-hat” tactics.

However, before we go through them one by one, it makes sense first to explain why an email might bounce back.

Let’s get into it.

Why Are Your Emails Bouncing Back?

In this part of our guide, we’re going to talk about some of the most prominent reasons why your emails bounce back.

Some are more common than others, but it’s likely that you have – or will –  come across most of them, so being aware of all of them is useful.

Let’s have a look at the first one.

Reason #1: Non-existent email address

One of the most common reasons why emails bounce back is that the recipient’s address hasn’t been found.

This can happen due to two reasons:

  • The email address doesn’t exist at all
  • The address has been misspelled

As you probably already know, each email address is unique, so should you send a message to an invalid email address then you’ll receive an auto-reply message from your email provider saying that the email account hasn’t been found:

Example of failed message delivery

If you believe that there aren’t any spelling mistakes in your recipient’s email address, then you should probably check if it’s still valid.

On the other hand, if you’re positive that the email still exists, you can check for possible errors such as:

  • Typos
  • Spaces
  • Special characters not followed by a letter
  • Special characters at the beginning or end

Plus, any other restriction email service providers might have when it comes to the local part, as well as the domain part of an email address.

Here’s what the basic structure of such an address looks like:

parts of an email

Overall, making sure that you’ve spelled your recipient’s email address correctly is an integral part of having your email message delivered and not bounced back.

Author’s Note: If you have an email list for your email marketing campaigns and want to avoid a high number of bounces, we suggest double-checking each new email you add for typos and other mistakes. A double opt-in usually fixes this.

 Let’s continue.

Reason #2: Your recipient’s inbox is full

Another reason why your email may be marked as undelivered is when your recipient has a full inbox.

Each email provider has a certain capacity when it comes to the maximum storage they can offer; should someone exceed that, they won’t be able to receive any new messages.

Since this is a soft bounce case – more on this later – it’s a temporary issue and there’s not much you can do on your side other than wait until your recipient’s storage has enough space again.

This is what a typical bounce-back message from your email delivery system will look like:

example of a full inbox
Image Source: Yamm

All in all, this is a common case of a delivery failure and we suggest contacting your recipient in a different way or simply waiting.

Let’s move on to the third reason.

Reason #3: Out of office/Auto-reply

Have you ever sent an email to a prospect and received an automated message saying that they’re out of office or “OOO”?

This is a common case when people with professional emails go on vacation or take days off; they simply set up an auto-reply message informing their email sender that they’ll be back soon.

What’s interesting about this is the fact that, although it’ll seem like your email has bounced back, it has actually been delivered and your recipient will see your message when they come back.

This is what an out of office automated reply typically looks like:

Out of the office automated reply example
Image Source: Small-bizsense

In that case, there’s not much you can do except wait until your email has been read.

If, however, you keep receiving the same auto-reply for a long period of time, you should potentially consider removing the contact from your email list in order to keep it clean.

Moving forward.

Reason #4: Blocked email

Another common reason that causes email bounce backs is blocked emails.

This is often the case with organizations such as government institutions or schools whose email servers are strict when it comes to receiving incoming emails.

In this case, this is the message you’ll receive based on your email service provider:

blocked email example
Image Source: Yamm

Another reason why a recipient’s mail server may be blocked is to prevent spamming attempts.

If the receiving server notices something suspicious on your side, this can potentially trigger spam filters which will cause your message to be blocked or end up in the spam folder.

A few key elements considered are the sender policy framework (SPF), which is an email authentication technique aimed at protecting users from spammers as well as how trustworthy your domain name system (DNS) is.

Author’s Note: We recommend paying attention to spam trigger words that you might have used in your email’s subject line or body.

To sum up, those are the most prominent reasons that cause bounce backs and undelivered emails; something with a great impact on the click-through and open rates of your cold email marketing efforts.

Earlier, we said that a full inbox is a clear case of a soft bounce; this is one of the two bounce types you should know.

Let’s have a look at them.

Types of Email Bounce

In this part of our guide, we’re going to talk about the two categories an email bounce back will fall into:

  • Soft bounce
  • Hard bounce

If you’re not familiar with the terms, no need to worry!

We’ll explain everything as clearly as possible.

Let’s get into it.

Type #1: Soft bounce

The first type of bounce is the soft bounce.

This is not as serious as the hard bounce and it means that your email was bounced temporarily.

To put it simply, when this happens, there isn’t an issue with your own or your recipient’s email address.

Common reasons that cause soft bounces are:

  • A full inbox
  • An out of office status
  • The email server is down or offline
  • The email message is too large

Plus, anything else that will cause a temporary issue or delay but will be fixed over time.

Let’s move on.

Type #2: Hard bounce

The other type of bounce is the hard bounce.

As you can imagine, this is slightly more serious than a soft bounce and a major problem for your email’s deliverability.

When this happens, your email has been permanently rejected by your recipient’s server for a number of reasons, such as:

  • An invalid email address
  • A non-existent email address
  • Blocked email

And any other reason that’ll cause your email to not be delivered at all.

Overall, those are the two bounce types that you need to be aware of every time you receive a non-delivery report or an error code.

No matter how easy or hard it is to solve a bounced email, the fact remains that it’ll affect your bounce rate.

Let’s see how you can calculate it.

How to Calculate Your Email Bounce Rate

To calculate the bounce rate for your email campaigns, you have to divide the total number of emails sent by the number of emails bounced.

You can then multiply the number by 100 to have the bounce rate expressed as a percentage.

Let’s assume you want to send a newsletter to all 1,000 subscribers on your email list.

If 10 of those emails bounce back, that will be a bounce rate of:

(10 / 1,000) x 100 = 0.01 x 100 = 1%

That’s a bounce rate of 1%.

Pretty simple, right?

Now you’ve just calculated your bounce rate and have the result in front of you, which in our case is 1%.

What does that mean?

Is it considered a “good” bounce rate? Should you be trying to lower it?

Those are most likely a few of the questions you’re thinking of right now, so let’s talk about them a little more.

What is an Acceptable Email Bounce Rate?

An acceptable email bounce rate for your email campaign is generally anything under 3%.

However, what you must keep in mind is that this can vary depending on the industry you’re in as well as the type of campaign you’re running.

For instance, the following image depicts the average hard bounce rate for a number of different industries.

Hard bounce rate graph
Image Source: Hubspot

As you can see, the average rate is significantly higher in the software field than in retail.

Nevertheless, if your bounce rate is higher than 3%, this is something that needs your attention and we recommend looking deeper into it.

Another factor to keep in mind is the type of campaign you’re running; an email marketing campaign makes sense to have lower bounce rates than a cold email campaign.


In the first case, you have a mailing list of subscribers who willingly gave you their email address while in the second case, you need to search for a prospect’s email online, which isn’t always as easy as it sounds.

What you can do, however, is use cold email software to help you find the right email addresses and make sure your bounce rates are as low as possible.

Let’s now have a look at more ways you can reduce your email bounce rates.

How to Reduce Your Email Bounce Rate

In this last section of our guide, we’re going to show you how you can reduce your email bounce rate.

If you’ve identified a higher-than-usual bounce rate in your own campaigns, then the following ways will come in handy.

Let’s get started.

Strategy #1: Use a double opt-in

Using a double opt-in system is a great way to make sure that your email list subscribers have actually given you the right email address.

This basically means that, when someone signs up to receive your newsletter, for example, you send them a confirmation email in order to validate their contact information before adding them to your list.

It’s something you’ve definitely encountered yourself, but the following example by Ahrefs will make the double opt-in process clear.

Assuming you want to subscribe to Ahref’s weekly digest, all you need to do is enter your email in their form…

Email sign up form
Image Source: Ahrefs

…you’ll then be notified that a confirmation email has been sent to your inbox…

Email sign up confirmation

…which will ask you to confirm your email by clicking on the “Yes, subscribe me to the list” button:

opt-in button

This will ensure that your email address list is correct and there’s no risk of the emails bouncing back.

As a result, Ahref’s email bounce rates can be significantly decreased.

Let’s move on to the second way.

Strategy #2: Authenticate your domains

According to research, less than 40% of brands use SPF, DKIM, and DMARC, which are common methods of email authentication.

Authenticating your email domain will mark you as trustworthy in the eyes of email service providers and will increase your deliverability rates, therefore decreasing your bounce rates.

It’ll also improve your email sender reputation that we looked at earlier; something that your recipient’s email server will take into account when receiving your message.

To sum up, we recommend that you authenticate your email domains by any means in order to keep your bounce rates as low as possible.

Moving forward.

Strategy #3: Clean your email list

While this may sound obvious, more often than not brands and marketers don’t regularly clean their email lists.

Over time, a list may become populated with inactive accounts or recipients with other issues which won’t allow your emails to be delivered to them.

Every now and then, it’s important to go through your list and remove any email addresses that increase your bounce rate.

You can do this by either requesting another opt-in or manually checking your email list for problematic accounts, although this could get time-consuming.

This will not only reduce your bounce rate but it should also increase the engagement rate and deliverability of your email campaign.

Let’s continue.

Strategy #4: Avoid spammy emails

Spam emails are a real problem nowadays.

According to Canada’s anti-spam legislation, over 5,000 Canadians every week made spam complaints during a five-month period in 2018.

What’s more, only 55% of all emails aren’t considered spam and contain legitimate content.

Percentage of emails that are spam
Image Source: Propellercrm

This means that you must try and avoid spam filters by all means, because if your emails end up in spam often, this’ll harm your sender reputation and will cause many of your emails to be undelivered.

Needless to say that you might even be put on a blacklist; a database that email providers have of potentially spammy and suspicious email senders.

You can avoid the spam folder by following a few simple tips, such as not using common spam words, not sending bulk emails, not having misleading sender information, plus many more.

The more email providers that trust you, the lower the chances of your email being marked and thus decreasing your bounce rate.

Overall, those are a few of the main ways you can reduce your email bounce rates.

Simply choose which ones are most suitable for you and get started!

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Now Over to You

There you have it.

That was our complete guide on email bounce backs.

We explained what this term means, why your emails bounce back, how you can reduce your bounce rates, plus many more useful insights in the world of email outreach.

We believe that you’re now ready to fix any potential problems you may have regarding the issue and take your email outreach to the next level.

However, if you need any help in your email outreach efforts then feel free to book a demo and we’ll make sure to guide you step-by-step.

Thanks for reading! 

Ivan Escott

Article by

Ivan Escott

Ivan is the partnerships manager at Respona, the all-in-one PR and link building tool that combines personalization with productivity. Along with creating content, he looks for unique ways to build meaningful relationships with other bloggers.

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