Crafting the perfect email—personalized, mobile-friendly, and spam-check approved—can feel pointless when it bounces back hard. A hard bounce occurs when an email is rejected outright by the recipient’s server, often because the email address is invalid or no longer exists. Hard bounces harm your sender’s reputation and can quickly lower deliverability rates. This article explores managing and reducing hard bounces to maintain high inbox delivery, maximize campaign success, and protect your reputation.

Inframail’s email infrastructure solution can help you achieve consistently high email deliverability rates by effectively managing and reducing hard bounces, maximizing campaign success, and protecting your sender’s reputation.

Table of Contents

• What is an Email Bounce?

• 6 Major Causes of Email Hard Bounce

• Can You Fix Hard Bounces?

• Managing and Reducing Hard Bounces

• Start Buying Domains Now and Setup Your Email Infrastructure Today

What is an Email Bounce?

An email bounce is a notification from a mail server that tells the sender an email wasn’t delivered. When an email bounces, it doesn’t reach the recipient’s inbox. Instead, the mailbox provider returned it to the sender. Have you ever mailed a package or a letter, but it was returned to you a couple of days later? 

Understanding Email Bounces: What They Are and Why They Happen

Maybe the package even included a sticker that provided more information on why your item wasn’t delivered. It might be that the address didn’t exist, you didn’t include sufficient postage, or the recipient refused to accept the package. Picture an email bounce as the digital equivalent of this scenario. Just like the post carrier uses stickers and stamps to categorize what went wrong with your letter, a mail server may reject your email with a diagnostic bounce code. 

What’s an Email Bounce Code?

Each time an email is sent using SMTP, the receiving server will respond with an SMTP code. For example, an SMTP response code 250 means the message was accepted and the delivery action was complete. But if the receiving server can’t complete the delivery, it will respond with an error code. Bounce error codes generally start with 4.X.X for temporary failures (soft bounces) and 5.X.X for permanent errors (hard bounces). We’ll go into more detail on those different kinds of bounces. 

Decoding SMTP Bounce Codes: How to Interpret and Address Email Delivery Failures

What’s handy about these SMTP responses is that they don’t just tell you there was a problem, but they also give you more detailed (and, in some cases, helpful) information on why exactly your email delivery failed. Every response code consists of a numerical bounce code and a description that provides more info on how the mail server uses that SMTP code. 

Here’s an email bounce code example:

smtp;550 5.1.1. The email account you tried to reach does not exist. Try double-checking the recipient's email address for typos or unnecessary spaces. Learn more at https://support.google.com/mai... - gsmtp

Thanks, Gmail. That’s quite helpful. If the email address doesn’t exist, we should not attempt to send it again.

What Are the Different Types of Email Bounces?

You can cluster bounces into two main categories: 

• Soft bounces occur when a temporary issue prevents your emails from getting delivered. 

• Hard bounces occur when there’s a permanent issue with delivering your email. 

Whether you’re seeing soft or hard bounces, there are many reasons why a bounce might occur—and whether and how you take action depends on what’s caused the bounce in the first place.

That’s why generalized advice like “if you’re seeing a hard bounce, do X. If you’re seeing a soft bounce, do Y” can be misleading. Instead, you’ll want to look at what has caused your emails to bounce (those bounce codes are handy for that!) and then tackle the root cause. 

What is a Hard Bounce? 

A hard bounce is a permanent failure of email delivery. It indicates that there will be no further attempt to deliver a message, and you must find a different way to reach the recipient. A hard-bounced email usually happens due to invalid email addresses typed in. Alternatively, a recipient’s ISP (Internet Service Provider) can reject your email for numerous reasons. 

What Is a Soft Bounce? 

A soft bounce is a temporary email delivery failure. Although an email failed to deliver this time, a server will often make further attempts later. Sometimes, all you need to do is wait. An email bounces softly when the recipient’s mailbox is full, either because one side hits some limits or an email message is deemed too large to accept. Notifications for out-of-office or other autoresponders are sometimes treated as soft bounces but work differently. 

Related Reading

• Why Are My Emails Going To Spam
• Email Deliverability Rate
• Email Monitoring
• Email Deliverability Issues
• Email Quality Score
• Bounce Rate in Email Marketing
• How To Avoid Email Going To Spam
• Why Do Emails Bounce
• SPF or DKIM
• How To Check If Your Emails Are Going To Spam
• Email Sender Reputation

6 Major Causes of Email Hard Bounce

1. Invalid or Non-Existent Email Addresses

Hard bounces frequently occur when emails get sent to invalid or non-existent addresses. This issue can arise due to multiple factors. Typographical errors are common, as email addresses are sometimes incorrectly typed, leading to undeliverable emails due to typos or formatting mistakes. For example, mistyping “user@example.com” as “user@exmple.com” will inevitably result in a hard bounce. 

Once valid, email addresses may no longer work. Users often change their email providers or deactivate their accounts, rendering their old addresses invalid. This is especially prevalent when people switch jobs or companies rebrand and update their email domains.

2. Non-Existent Domains

Emails can also bounce if they are sent to domains that do not exist. This problem typically arises from misspelled domains, where even a tiny domain name typo can invalidate the entire email address. For instance, sending an email to “@gmial.com” instead of “@gmail.com” will result in a hard bounce. 

Deactivated domains also contribute to this issue. Domains that were once active but have since been deactivated or allowed to expire will cause emails to bounce. This scenario is typical for business domains shut down due to the business closing or merging with another entity, thus changing their domain names.

3. Blocked Email Servers

Modern mail servers reject tons of emails they suspect of being unwanted, causing deliverability issues and impacting your sender’s reputation. And while they’re almost always right to do so, sometimes the spam filters get rid of legitimate emails without hesitation. The reasons for this can be many. 

Often, a lack of proper authentication plays a role, so ensure you have set up SPF, DKIM, and DMARC. Check also if you have PTR Records set up and if they match A record from your domain’s DNS. Review Google and Yahoo’s new sender guidelines and ensure your sending practices align with all the requirements. 

Improving Email Deliverability: How User Behavior and List Management Impact Inbox Placement

To improve the experience of its users, ISPs also look at their past behavior when determining whether an email should be accepted or not. If you keep sending emails, but recipients never care to open them, a receiving server may finally reject them before they reach an inbox to save them the trouble. For that reason, it’s good to clear your mailing lists occasionally and manually unsubscribe inactive contacts. 

If none helps and your emails bounce, it’s worth seeking support. If you experience problems with a particular domain, contacting them directly might get you whitelisted for future deliveries, improve your email deliverability, and reduce the chances of emails going to the spam folder.

4. Spam Filters and Content Filtering

Emails that trigger spam filters can result in hard bounces. This can occur due to various factors. Suspicious subject lines or content that appear spammy or contain trigger words like “free,” “urgent,” or “win” can cause emails to be flagged and subsequently bounced. High volumes of spam reports also contribute to this issue. 

If recipients frequently mark your emails as spam, future emails may be automatically filtered out and bounced back. This underscores the importance of crafting thoughtful, genuine email content that resonates with recipients and avoids common spam triggers.

5. Full Mailboxes

While typically causing soft bounces, persistently full mailboxes can lead to hard bounces over time. This situation indicates inactive mailbox management, where the recipient is not actively managing their mailbox, leading to it being perpetually full. 

Over time, some email servers may consider such addresses invalid after repeated failed delivery attempts. This is particularly relevant for recipients who do not regularly check or clean their email inboxes, allowing them to reach their storage limits and subsequently causing emails to bounce.

6. Challenge-response error

This error is slightly different from its predecessors on our list. Some people set up an additional firewall meant to authenticate senders. Sometimes, email providers set those up by default, too. When you email such a contact for the first time, you’ll get an automatic response. Usually, you’ll be asked to answer a question or perform some action to verify that you’re a legitimate sender. 

Once you do, your email will be delivered. If you ignore this email and a few days pass, your email will bounce. The only thing you can do to avoid it is to complete the challenge well. The good news is that in most cases, once you prove you’re a homo sapien, you won’t have to repeat this boring routine.

Related Reading

• DMARC vs DKIM
• Importance Of DMARC
• What Is a Soft Bounce Email
• Email Deliverability Checklist
• What Affects Email Deliverability
• Why Is Email Deliverability Important
• Email Bounce Rate
• Fix Email Reputation
• Improve Sender Reputation
• Email Deliverability Tools
• Email Deliverability Best Practices
• Best Email Domains

Can You Fix Hard Bounces?

Hard bounces significantly hurt your sender’s reputation, which measures your credibility as an email sender. 

Here’s how:

ISP Monitoring

Internet service providers (ISPs) closely monitor bounce rates to determine the quality of email senders. A high rate of hard bounces indicates to ISPs that your email list contains many invalid addresses, suggesting poor list management practices. 

Domain Flagging

When ISPs detect consistently high bounce rates, they may flag your domain as a source of unwanted emails. This can lead to your emails being automatically filtered into spam folders or blocked entirely. 

Blacklisting

If your domain is flagged repeatedly, it can be added to email blacklists maintained by ISPs and anti-spam organizations. Being blacklisted severely hampers your ability to reach recipients and can require significant effort to rectify. 

The Direct Connection Between Hard Bounces and Email Deliverability 

High bounce rates directly reduce your email deliverability. This occurs in several ways:

Spam Folder Diversion

Emails from domains with high bounce rates are more likely to be diverted to recipients’ spam or junk folders, significantly lowering the visibility of your messages. 

ISP Filtering

ISPs may employ stricter filtering rules for domains with poor sender reputations, reducing the likelihood that your emails will reach the intended inboxes. 

Reduced Sender Score

Your sender score, a numerical representation of your email-sending reputation, will decrease. A lower sender score reduces deliverability rates as ISPs become more cautious about email acceptance. 

The Cost of Ignoring Hard Bounces 

Sending emails to invalid addresses is costly and wasteful in several respects:

Resource Allocation

Each undeliverable email represents wasted resources, including the costs associated with: 

• Email marketing services

• Bandwidth

• Data storage

Design and Targeting Efforts

The time and effort spent designing email campaigns and segmenting lists are squandered when emails fail to reach valid recipients. This inefficiency can strain marketing budgets and resources. 

Operational Costs

High bounce rates may lead to increased costs from email service providers (ESPs), who charge based on the volume of emails sent or penalize high bounce rates. 

How Hard Bounces Affect Campaign Performance and Engagement Rates 

Hard bounces adversely affect the performance and engagement metrics of your email campaigns:

Lower Open Rates

A high number of hard bounces reduces the overall number of emails in recipients’ inboxes, leading to lower open rates. This diminishes the effectiveness of your campaign in engaging your audience. 

Reduced Click-Through Rates

With fewer emails being delivered and opened, the click-through rates (CTR) on your calls to action also decline. This impacts your campaign’s ability to drive traffic, conversions, or other desired outcomes. 

Negative ROI

As engagement metrics drop, your email marketing campaigns’ overall return on investment (ROI) suffers. Lower engagement means fewer conversions and a diminished ability to achieve marketing goals. 

Can You Fix Hard Bounces? 

The short answer is no. 

“Fixing” hard email bounces is a tough ask. As we said, hard bounces are caused by permanent issues that probably don’t go away. Some good things to do if you’re experiencing a lot of hard bouncebacks are ensuring you comply with email authentication standards like SPF and DKIM and avoiding triggering spam filters by following best practices. The number one defense is maintaining a clean and engaged email list by regularly removing inactive or incorrect addresses and implementing things like sunset policies to help guide you in reviving or removing non-engagers. 

Why You Should Stop Sending Emails to Hard Bounce Addresses

Because it would hurt your sender’s reputation if we did! Sending an email that doesn’t exist to Gmail tells them that you might not be a legitimate sender and, in turn, makes you look like a spammer. Whether you’re seeing a lot of hard bounces with triggered transactional email messages or in your latest email marketing campaign, it’s best to cut them out entirely.

Managing and Reducing Hard Bounces

Regular Email List Cleaning and Validation

Cleaning your email list is crucial for lowering hard bounce rates. Hard bounces occur when emails get returned to the sender because the recipients can’t be reached. This is usually due to invalid addresses resulting from typos, closed accounts, or blocked servers. The best way to prevent hard bounces is to eliminate invalid addresses before you send your email campaign. Regular email list cleaning and validation will help you maintain a healthy list to improve email deliverability. 

The Importance of Email Validation: How Regular List Cleaning Enhances Deliverability and Reduces Bounces

Email validation services are valuable tools that check email addresses for accuracy, catching typos, invalid domains, and inactive addresses. These services ensure your list only includes valid contacts, lowering bounce risks. Automated list cleaning every so often is vital. It removes old or inactive addresses, preventing a buildup of invalid ones. Manual verification might be necessary for essential contacts. This step involves sending a personal email to confirm the address is still active and correct. Although more time-consuming, it’s key for maintaining accurate business contacts.

Implementing Double Opt-In for Subscriptions

Using double opt-in for subscriptions is smart. This approach requires subscribers to confirm their email address twice. First, they get a confirmation email. Then, they must click a link to confirm. This method ensures they entered a valid email address and are genuinely interested. It cuts down on fake or incorrect email addresses. Plus, it boosts engagement by showing genuine interest. While it might lower subscriber numbers, it improves the list’s quality. This, in turn, enhances email deliverability and campaign success.

Monitoring Bounce Reports and Taking Action

It is key to regularly check bounce reports and act on them. These reports show how your email campaigns are doing and highlight problems. Studying certain email addresses or domains can help you spot patterns. Quickly fixing addresses causing hard bounces is crucial. This protects your sender’s reputation and ensures your emails reach the right people. Setting up feedback loops with significant ISPs is also essential. It helps you respond quickly to complaints and bounces, improving your sender’s reputation and delivery.

Using Email Authentication Protocols (SPF, DKIM, DMARC)

Using SPF, DKIM, and DMARC in emails boosts their verification and delivery. SPF limits where emails from your domain can come, thus stopping spam. This action improves email trust. DKIM adds a digital signature to show emails are genuine and unaltered. DMARC steps in by deciding how servers treat emails that fail verification. It also provides verification reports, highlighting potential issues and enhancing email security.

Segmenting Email Lists Based on Engagement

By ranking subscribers’ engagement, you send emails to active ones. Focusing on those who open and click often reduces bounce risk and lifts campaign success. Reviving interest in inactive subscribers is key. If they stay inactive, consider removing them. This keeps your list effective. Segmenting based on behavior can boost targeting. Aligning segments with recent purchases, site visits, or interests makes emails more engaging and lowers bounces.

Related Reading

• Email Monitoring Software
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• Check Email Deliverability Score
• Soft Bounce vs Hard Bounce Email
• SalesHandy Alternatives
• GlockApps Alternative
• MailGenius Alternative
• MxToolbox Alternative
• Maildoso Alternatives

Start Buying Domains Now and Setup Your Email Infrastructure Today

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It scales its cold email outreach efforts efficiently:

• Agencies

• Recruiters

• SDRs    

Email Deliverability without the Headaches  

Inframail provides automated SPF, DKIM, and DMARC setup to help you reach more prospects without the usual technical hassles and costs. Whether you are an agency looking to scale outreach, a recruiter connecting with candidates, or an SDR driving sales, you need a robust email infrastructure to reach your goals. Inframail streamlines the entire process. We handle the complex infrastructure setup while you focus on your outreach efforts.