What Are Email Bounces: How To Reduce Bounce Rates And Improve Email Deliverability

2 minute read

Ever found yourself scratching your head over an email campaign that didn't perform as expected—because a good number of your emails bounced back? If so, you're not alone. 

Understanding email deliverability and how email bounce works can significantly improve the performance of your email marketing efforts. 

In this article, we shed light on email bounce rates, the difference between soft bounce and hard bounce, email marketing automation's role in managing bounces, and some practical tips to enhance email deliverability.

Why does an email bounce? 

An email bounce occurs when an email can't be delivered to the recipient's inbox and is sent back to the email service provider (ESP). To understand why an email bounces, we need to understand how emails are routed.

When you send an email, it doesn't go straight to the recipient's inbox. 

Your email starts its journey by traveling to a special program called a Mail Transfer Agent (MTA). This program uses a protocol called Simple Mail Transfer Protocol (SMTP) to send the email on its way. Think of it like handing your letter to a postal worker who follows specific rules (SMTP) to get it delivered.

email bounces
Image source

Just like a mail carrier needs an address, the MTA needs to know where to deliver your email. It uses a Domain Name System (DNS), which acts like a giant phonebook for the internet, to find the recipient's email server. Similar to checking a zip code, the MTA uses a specific record called a Mail eXchanger (MX) record to find the right server.

Once the address is confirmed, the receiving server scans the email for any harmful content like viruses. If everything is safe, your email finally reaches its destination—the recipient's inbox!

So, there can be many reasons causing your emails to bounce. To fix the problem, you first need to know what percentage of your emails are bouncing and why—which leads us to email bounce rates and bounce codes.

What are email bounce rates and bounce codes?

The email bounce rate is a key metric in email marketing automation, and it refers to the percentage of your emails that are not delivered to the recipient's inbox.

A high bounce rate is often a sign of problems in your email list or issues with email deliverability. If the issue is email deliverability, it can be due to various reasons, such as lack of domain authority, un-warmed mailboxes, bad subject lines, and more. 

If your email bounce rate is too high, your mailbox service provider (MSP) can penalize you for your poor sender reputation. From the MSP's lens, your bounce rate indicates the quality of your email list and its health.

So, the recommendation is to keep your bounce rate under 2%

Why not go for a zero bounce rate, you ask? 

That's the aspiration, but it is not always realistic. Emails will bounce for one reason or the other—people change jobs, companies get acquired, domain names change, and more.

Some bounces are temporary issues and have nothing to do with maintaining a clean contact list. Even a full mailbox could cause bounces.

Improving email bounce rates starts with bounce rate analysis, i.e., regularly reviewing your email campaign reports to identify which emails are bouncing and why. 

You can track your bounce rate in one of the following ways: 

  • Check your email service provider's statistics. Most providers share data on bounces, including the percentage of emails that bounced and the reason for the bounce. Here’s an example of average bounce rates benchmarked by industry (published by Mailchimp)
  • Catch-all inbox. People sometimes guess emails of recipients by using variations of someone's name or company, and try sending messages to those emails.These guessed emails typically land in a special inbox called a "catch-all" if your email provider has one. Think of catch-all as a giant mailbox that receives anything addressed to their domain, even if the specific name is wrong. This way, they might catch your "johndoe" email and ensure important messages don't get lost. 
    While convenient, catch-alls can also receive spam or unwanted messages. And that is why the Plena bot scrutinizes every email coming from any provider (no matter how reputable) to avoid inbox clutter.
  • Use an email automation and tracking tool. These tools can give you detailed information on your bounce rate, including which specific emails bounced and why. 

If you see a sudden drop in open rates or click-through rates, that could indicate that your bounce rate is increasing.

So that takes us to understanding the different email bounce codes.

Email bounce codes

When an email cannot be delivered to its intended recipient, the receiving server returns an SMTP (Simple Mail Transfer Protocol) response code to the sender. This code, known as the email bounce code, indicates the reason for non-delivery.

There are primarily two types of email bounces, delineated by their respective bounce codes: soft bounces and hard bounces. 

If you use email automation tools, a drill-down on your bounced emails might look like this👇

Soft Bounce vs Hard Bounce

Soft bounces

Soft bounces are temporary delivery failures identified by SMTP codes starting with 4.X.X. The causes of soft bounces are usually temporary and can often be rectified with subsequent attempts.

Common reasons for soft bounce emails include:

  • The recipient's mailbox is full
  • The mail server is temporarily down or offline 
  • The mail server or mailbox is temporarily overloaded (receiving too many messages at the same time) 
  • The email is too large for the recipient's inbox 
  • The message does not meet the receiving server's requirements for authentication or sender credentials

By understanding and addressing the reasons behind soft bounces, you can significantly improve email deliverability and minimize their email bounce rate, enhancing the overall performance of your email marketing campaigns.

Hard bounces

A hard bounce is indicated by codes starting with 5.X.X representing permanent delivery failures. This can occur when a person has moved companies, and an email is now invalid, or simply when someone enters a junk email onto your form.

Causes for hard bounces often point to the hygiene of your email lists, as hard bounces often occur due to the non-existence of the recipient's email address or invalid email addresses or domains.

A few other reasons include the following:

  • Authentication issues
  • Low sending domain reputation or your domain or IP address is on a spam blacklist 
  • Your sending domain is blocked by receiving mail server rules
email bounce
Source: Klaviyo

Addressing hard bounces and improving email deliverability requires maintaining an up-to-date email list and employing verification processes at sign-up to minimize errors and maximize the efficiency of email marketing campaigns.

Does hard bounce and soft bounce impact domain reputation?

Yes—there's a correlation between email bounce and domain reputation. In case of a hard bounce, it's best to delete the contact or stop sending emails to that address, as it impacts your domain reputation. However, for soft bounce, you can retry several times in the next campaign without damaging your domain reputation. 

Now, let's go beyond damage control. Let's look at a few things you can do to improve your email deliverability.

Strategies to improve email deliverability

To combat email delivery issues and improve deliverability, consider implementing the following strategies:

Email list hygiene

Regularly clean your email list by removing invalid or non-engaging email addresses to minimize the risk of getting flagged as a spammer. Using email validation tools helps in identifying invalid email addresses on your list as they do:

  • Syntax checks: Checking for typos, missing characters, or incorrect formatting.
  • MX record verification: Confirming if a valid mail server exists for the domain in the email address.
  • Disposable email detection: Identifying temporary email addresses used for signup and avoiding sending to them.

By removing these invalid addresses, you improve your deliverability rate, ensure your emails reach real inboxes, avoid bouncing back, and maintain a good sender reputation with email providers.

In fact, using a tool like Plena is highly recommended because it not only has Debounce embedded in its process for email validation, but also helps you build a high quality email list using intent data

Intent data is the information trail created by a prospect or lead. It consists of key behavioral signals that can be aggregated and analyzed to determine how likely a prospect will buy your product and when that transaction might occur. 

For example, Plena looks at multiple attributes (sometimes 22 or more) to determine if someone is consuming content casually or has a specific need with a high buying intent. In fact, with Plena, the entire cycle from building your contact list to outreach across multiple channels can be completely automated.

email delivery

So, when you build a target email list with high buying intent and understand what they might be looking for—you'll build in the relevance. Therefore, the chances of your email landing in their primary inbox and getting a response are high.

Improve domain reputation and warm up email domains before starting email campaigns

Improving the reputation of your domain involves authenticating your emails with SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) records. These technical settings help to verify that the sender is legitimate and thus improve deliverability.

Additionally, gradually warming up a new email domain by slowly increasing the email volume can help build a good sender reputation and avoid ISP (Internet Service Provider) blocks.

Domain warming is training your domain and building a reputation as a trusted sender. If you start sending 100s of emails in the early days of your domain, they will mark it as suspicious by default. It typically takes 8-12 weeks to accomplish maximum deliverability. 

email deliverability

So we recommend the following best practices:

  • Don't set up more than one email account in the first month. 
  • By the second week, send out simple conversational emails (not more than 2-3 per day) to the business emails of your contacts who will reply. The reply rates matter a lot, especially if your email provider is Gmail.
  • It's best to set up your recipient emails with different email providers, such as AOL, Yahoo, Yandex, Gmail, Outlook, etc.
  • Once you do this for 2 weeks, you are ready to run a test campaign. You can build a list of 20 emails that you trust won't bounce (ideally those who will respond to you) and run a test campaign using Plena.
  • Increase the number of emails gradually. Remember that even if your domain is old enough and has an excellent reputation, sending campaigns in huge numbers may impact your domain's credibility.

Use Double Opt-in

Encourage new subscribers to confirm their interest to join your list with double opt-in.

Double-opt-in means—a prospect first signs up for your email list and then confirms their subscription via email. It's an additional step but worth the hassle as it ensures everyone on your list is interested in hearing from you. 

It helps avoid any potential spam complaints in the future.

Double opt-in helps improve your open and click-through rates, improving email deliverability.

Avoid using spammy language 

It may sound obvious—but you may be using spam language in your emails unintentionally. Email service providers like Gmail and Yahoo often look for specific words, images, or phrases in content to mark emails as spam. 

For instance, you might want to avoid subject lines like these at all costs 👇

❌ Quick question

❌ <First name>, want xyz?

❌ Thoughts? (And any of the cliches)

❌ RE: (screams "shady")

❌ 2x/10x revenue/conversion or anything merely transactional

Also, if you're using words like "Act Now," "Free Offer," or "Make Money," there's a good chance that your email goes straight to the junk folder.

Segment your email lists based on engagement

Segmenting allows you to send personalized and targeted emails to subscribers more likely to interact with your content, resulting in a higher overall open rate.

On that note, you might want to look at the post below 👇 if you would like to improve your email open rates.

Common errors that kill email opens

Paying attention to subscriber engagement and feedback is key. If recipients frequently mark your emails as spam, this will harm your sender reputation and email deliverability. Encourage feedback from your subscribers and adjust your email campaigns accordingly to ensure they are always engaged and satisfied with the content you provide. 

Furthermore, implementing an easy unsubscribe process can help maintain a cleaner email list and reduce the risk of being marked as spam.

Wrapping up…

The problem isn't your email bounces; it's what's causing them in the first place. If your bounce rate is high, it must be fixed immediately. Ideally, your bounce rate needs to be under 2%, and if it's above that threshold, you might be facing deliverability issues.

Your email deliverability, in turn, hurts your reputation as a sender, causing a decrease in engagement levels, email open rates, and lower click-through rates. And they collectively impact your pipeline and, consequently, revenue.

We hope this post helped you with some methods to improve your email delivery and reduce email bounces.

Each day without Plena = Lost Sales

With Plena — list building, contact enrichment and scalable multi-channel outreach is a breeze.