Email Bounce Backs – What Are They and How to Fix Them


Email bounce-backs are an essential metric to understand in your email marketing strategy. Email bounces happen to everyone. Sometimes they can be avoided, and sometimes they can’t. Either way, you want to try to keep bounces as low as possible.

It’s important to understand the different types of bounces that exist and why they happen. This will help you do everything you can to prevent them, which will help your email campaigns achieve better results.

Follow this guide for everything you need to know about email bounces and how to avoid them.

  1. What are Email Bounce Backs?
  2. Email Delivery Steps
  3. The 3 Types Of Bounce Backs
  4. Why Do Emails Bounce?
  5. How to Identify an Email Bounce Back Message
  6. What is an Email Bounce rate?
  7. How to Calculate Email Bounce Rate
  8. How to Fix Email Bounce Backs
  9. Frequently Asked Questions

What are Email Bounce Backs?

Email bounce-backs are when emails are sent out but are not delivered to the recipient.

Email service providers send out automated email bounce-back communications to let the sender know that their emails haven’t been successfully delivered to the intended recipient. This is also known as a Non-Delivery Report (NDR), and it should inform the sender about what caused the delivery failure of the email.

An email bounce error message is a typical part of email marketing. Some email bounces are to be expected with each email campaign you send out, and that’s OK. However, you shouldn’t just accept email bounces whenever they happen. After all, your goal is to get as many emails as possible into your recipient’s inbox.

Email Delivery Steps

To understand how and why email bounces happen, it’s important to first know the different steps it takes to deliver an email:

  1. You send an email by addressing the “From” and “To” fields
  2. The email goes through your Simple Mail Transfer Protocol (SMTP) server for it to be sent out for delivery
  3. Before sending the email, your SMTP server checks your email with the Domain Name Server (DNS). The DNS is the address book that holds information on domain names and servers’ IP addresses
  4. The DNS locates the email recipient’s server. Now the SMTP server sends your email message to the recipient’s Mail Transfer Agent (MTA) which is what completes the delivery of the email
  5. Now the email is delivered to the recipient’s inbox

This is the ideal flow of events. However, there are some cases where the email is not successfully delivered during the last step. This is where bounce-backs come into play.

The 3 Types Of Bounce Backs

There are three types of email bounce-backs that could occur. These could either be temporary or permanent.

In order to troubleshoot these issues, it’s important to understand which email bounce category you’re dealing with.

1. Soft Bounce Emails

Soft bounces happen when the email server rejects an email temporarily.

These types of bounces are no trainwreck, and they can be amended at a later stage. In fact, many email services will try to resend an email message after a soft bounce.

Common causes of soft bounces include:

  • Full mailboxes
  • The email is too large
  • Unreachable servers
  • Autoreply messages turned on

2. Hard Bounce Emails

A hard bounce is when your email is permanently unable to send to a certain address.

When you experience hard email bounces, you should try to remove the email address from your mailing list straight away. This won’t fix hard bounces, but it will improve your bounce rate and help prevent your email address from being blocklisted.

Common causes of hard bounces include:

  • Fake email addresses
  • Incorrect email addresses
  • Blocked emails

3. Blocklisted Emails

Email blocklists are when your emails are blocked by email servers. This typically takes the form of spam complaints, where your email is directed to a spam folder instead of the inbox.

These lists are created by Email Service Providers (ESPs), and you want to avoid being on them at all costs! It’s important to understand that these lists are designed to protect the recipient from spam or malware attacks, and they’re not just there to make your job as an email marketer more difficult.

Common causes of blocklisted email bounces include:

  • Spam complaints
  • Having consistently high bounce rates
  • If your email list grows too fast (a sign of buying subscribers)
  • Sending bad content and spammy words

Being on an email blocklist is not ideal. It could mean a slight dip in your email marketing results, or it could totally affect the results of your email campaign.

If you find your email address on a blocklist, you can try the following strategies to get off the list:

  • Send quality content and hope to be automatically removed from the list over time
  • Submit a request to be delisted from the blocklist. You can send this to the blocklist holder’s website
  • Try to keep your bounce rate low by removing email addresses that consistently cause hard bounces
  • Send valuable email content to the right people to avoid spam complaints
  • In worst-case scenarios, you may have to change your ISP if your IP is compromised

If you find that you’re on a blocklist, it means there’s something wrong with your email campaigns. If this is the case, it’s time to assess who your audience is and whether you’re sending them the right content. Also, pay attention to your email marketing metrics and take note of which emails receive the highest unsubscribe rates or complaints of spam.

Top Tip: Never ever buy email subscribers. This is just a bad email marketing practice, and it’s a one-way ticket to being sent straight to a blocklist

Why Do Emails Bounce?

There are various reasons why email deliverability issues occur. The good news is that many of these issues are easily fixed.

Here are some of the most popular reasons why bounces happen o your email blasts.

1. Incorrect Email Address

This is one of the most common, and simple, reasons for a bounce back. It happens when there is an error in the email address, such as a typo. It could also happen if the recipient is no longer using the mail ID.

This type of bounce back can be identified if the bounce was listed as a “non-existent email address”.

To fix this, go to the email address and check it for any missing characters or spelling errors. If you can identify an issue, then fix it. If not, then remove the email address from your list (as emails sent to this address will always bounce).

This could happen if the email address was inputted incorrectly, or if the user provided a fake email address on purpose. It could also happen if the user changed over to a new email address and the one you have is outdated, or if it’s a corporate ID and the user has left the organization (and their email address is blocked).

2. Full Mailboxes

Mailboxes have storage limits. If the recipient’s mailbox is full, then your email will fail to be delivered.

This is a temporary issue and it isn’t your fault. The recipient’s mailbox server will bounce every email sent to the address.

One thing you can pay attention to is the size of your emails. If you include attachments or images, always try to compress these emails before sending them. This means your email will take up less space, so it might still be able to squeeze into nearly-full mailboxes.

You can easily do this with a compressor tool.

If your email is loaded full of attachments and images, you could also break this up into a series of emails.

Keeping your email content short and condensed is always a good idea.

3. Blocked Emails

Some email recipients only allow specific IP addresses to deliver emails to them. This is done for email security issues, or to limit the number of emails received by a prominent email address.

These IP restrictions commonly happen with government organizations, schools, or certain corporate IDs. If your emails are constantly being bounced by these corporate IDs, then you will need your IP address to be whitelisted by the organization’s mail servers.

Try contacting the organization through an alternative email address to address this issue.

4. Auto-Response Emails

This is a unique type of email bounce that typically happens when the recipient is out of the office or on vacation. The recipient will set up an auto-response email that sends as soon as your email reaches them.

The good news is that you only ever receive an auto-reply email if your email lands in the recipient’s inbox – so this isn’t necessarily a bad thing.

Just pay attention to these emails and ensure it’s only a temporary issue. If you continue to get auto-response emails for months, then the mailbox has probably been abandoned or the recipient never checks their emails.

If this is the case, it’s probably best to remove the email address from your bulk mailing list.

5. The Recipient Blocked Your Email Address

This is a bad type of email bounce that you want to avoid at all costs. It happens if the recipient doesn’t like the type of content you’re sending or is tired of seeing your emails land in their inbox. In this case, they mark your emails as spam complaints, or simply block your address.

If the recipient blocked your address, an automatic email bounce will happen.

To address this, you want to make sure that you’re sending out high-quality content to the right people (more on this later). You also need to have a working unsubscribe link clearly visible on each email you send.

This will help your unwanted subscribers to rather opt-out than block you. If this is the case, your bounce rate won’t be affected.

6. Recipient Server Issues

Undelivered emails could also happen if the recipient’s mail server has issues. The problem is on their side, not yours, so there’s nothing you can do to fix this.

The recipient’s server could have crashed, it could be going through maintenance, it could be overloaded, or experience downtime. Whatever the case, this issue is temporary, and your emails should be able to get through again.

Try to resend these emails at a later stage. If the problem continues over a long period of time, then consider removing the email address from your bulk list.

7. Other Factors

These are the main reasons why email bounce-backs tend to happen. However, there are cases where bounces can happen due to other unknown reasons.

The general rule is that you should monitor any IP addresses that experience consistent bounces. If the issue continues to happen over an extended period of time, you may want to stop sending emails to this address.

How to Identify an Email Bounce Back Message

You will receive an email notification when your emails fail to send. It will typically look like this:

email bounce backs

In most cases, the email service provider will give you a reason why the bounce-back occurred. Most major email service providers will also provide recommendations to fix the email deliverability issue.

Go back to the list above to identify the types of email bounces and understand how to respond to them.

What is an Email Bounce Rate?

Email bounce rate is an important email marketing metric to know. It’s shown as a percentage and represents the total number of emails that have bounced back in relation to the total number of emails that you have sent.

Most email marketing services should display the bounce rate of your email campaigns.

How to Calculate Email Bounce Rate

Bounce rate can be calculated through the following steps:

  1. Take the total number of emails sent
  2. Find the total number of bounce backs
  3. Divide the total number of emails sent by the total number of bounced emails
  4. Multiply the result by 100 to get a percentage

What Should Your Email Bounce Rate Be?

While email bounce rates vary a lot between different industries, you ideally want to keep yours below 10%. This is a good general aim.

Businesses can set their own bounce rate KPIs based on their lists’ historical performance. In many cases, it is achievable to get a 3-5% bounce rate, which is excellent. This is something many Wishpond eCommerce clients are able to achieve.

How to Fix Email Bounce Backs

You can’t always fix email bouncebacks, but you can reduce the likelihood of them happening. To improve the success of your email marketing campaigns, you’ll want to try to keep your email bounce rate as low as possible.

Here are some of the main ways to fix email bounces or reduce the chances of them taking place.

1. Clean Your Mailing Lists

Keeping your mailing lists clean is one of the best ways to reduce bounces. Clean means that only email addresses that don’t cause bounces are on your list.

Regularly check your mailing list and remove any unengaged or abandoned email addresses. Some email platforms might remove hard bounces automatically. If yours doesn’t, then you’ll need to pay careful attention to removing these addresses as soon as you identify them.

A clean mailing list will keep your bounce rate low. While this won’t fix hard bounces, it is important for improving deliverability.

2. Use Permission-Based Lists

Consider using a double opt-in email process to make sure that the people on your list have made it clear that they want to receive emails from you. Always ensure that your subscribers have given clear consent to receive emails from you.

If not, you will see a rise in spam complaints and unsubscribes. This will increase your bounce rate.

email permission based lists

3. Send Emails Consistently

Daily and historical sending volume are important factors in the health of email accounts. Businesses should aim for steady volume as much as possible to help their email bounce rate.

Sending emails regularly will help you to generate higher levels of engagement and reduce your spam complaints. This will mean lower bounce rates in return.

Just make sure you don’t overdo this and send emails excessively. Sending out emails two to three times a week is generally the best practice. You could also send emails every day. Whatever the case, choose your sending schedule and keep it consistent. Inconsistent email sends could also trigger spam filters.

4. Authenticate Emails

Email authentication is another good strategy to make sure your reputation as a sender stays strong. Most email marketing services should allow you to automatically authenticate emails, which will help you achieve more consistent email deliverability.

5. Allow User Preferences

An important strategy to reduce email bounce-backs is to make sure your subscribers only ever receive the kind of content they’re interested in. An effective way to do this is by offering user preferences.

When a subscriber signs up for your mailing list, you can give them the option of what kind of emails they want to receive. This way, they know what to expect which reduces the chances of spam complaints.
email user preferences
Image: Freshmarketer

6. Use List Segmentation

Another effective way to improve deliverability is to use lead segmentation. Create lists of your most engaged email subscribers (those who have clicked and opened your emails recently) and send these subscribers your email first. This email list will result in better engagement, which is a positive sign for ESP spam filters.

Then, send your emails out to the more unengaged lists. Chances are, your positive email engagement from the list before will give your email to unengaged subscribers a boost.

You can take this even further by segmenting your lists based on interests and demographics. This will help you send more relevant, personalized content to each list. Personalization improves email engagement to help reduce hard bounces.

Segmented email lists

7. Use Email Verification

Email verification is the process of checking that an email address exists and is valid. A verified email is one that can receive emails from another email address.

Email verification ensures you only send out emails to addresses that work. This will instantly reduce any hard bounces.

Email verifiers perform multiple steps of the verification process. These are generally syntax, domain, catch-all, and MX record checks.

Wrapping Up

Emails bouncing are normal reasons that prevent people from opening your emails, but you don’t ever want to let your bounce-back rate get out of control. Avoiding hard bounces wherever possible, and doing what you can to reduce the chances of a high bounce rate is essential for effective email marketing.

Luckily, this is pretty easy to achieve. By using the right email marketing platform that gives you more control over your campaigns, you can make small changes to help improve your bounce rate. This will have a major positive impact on the results of your email campaigns.


Frequently Asked Questions

Why is My Gmail Bouncing Back?

It could be because of many reasons, such as an incorrect email address, server issues on behalf of your recipient, your email address being blocked, and more. Gmail should send you an email bounce notice stating why the email failed to deliver.

Why Does an Email Bounce?

Emails typically bounce due to the following reasons:

  • Incorrect or fake email address
  • Full mailboxes
  • Blocked email addresses
  • Auto-response emails
  • Recipient server issues

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