Soft Bounce vs. Hard Bounce: Email Delivery Issues and Its Effects in Digital Marketing

Soft Bounces 101

When speaking of a “soft bounce” we are referring to a temporary problem that causes an email to not be delivered to the recipient's inbox. Most times, the sender receives a notification of this. Some common reasons for a soft bounce are:

• A full recipient inbox. Until the recipient clears their inbox, the email server won’t accept any new message. Though no direct action is required, if a soft bounce continues for several messages, consider reaching out to your customer for a new address, or removing the email from your list.
• The recipient’s email server is down. In those cases, when the email bounces you can receive a message saying: “Service unavailable: Server is temporarily offline.” Usually, this sort of bounce is due to an overloaded system, as well as by maintenance or outages. Waiting for the server issue to be solved (48-72 hours) and retrying to send the email often does the trick.
• An excessively large message. If a customer’s email provider (or yours) has a size limit of 10 MB and you send a 15 MB attachment, the email will bounce. You may even receive a response saying: “Message rejected: Exceeds maximum size limit.” To avoid this, ensure that images and attachments are optimized for email size limits. Some means to achieve this are reducing the size of attachments, compressing images, and using cloud links for large files.
• Temporary flagging as spam. Suspicious emails are often flagged as spam, as a security measure. Most times, this can be prevented by avoiding spammy subject lines or content (like specific keywords or excessive usage of links). Authenticating your emails using SPF, DKIM, and DMARC also helps to strengthen your sender reputation, reducing the risk of ending up in the Spam folder.
• Issues with the domain's DNS settings or MX record. Misconfigured email settings and DNS complications may cause your emails to be temporarily rejected by the recipient's server. You can prevent this by regularly reviewing and updating your email authentication protocols (SPF, DKIM, DMARC) and DNS configurations. Only retry sending the email after resolving any detected issues.

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Email Deliverability & Soft Bounce

Since those issues are temporary, a soft bounce is not graded as harshly by Internet Service providers. Nonetheless, soft bounces do affect email deliverability in several ways, depending on the type and frequency of the bounces.

Extensive bounces, even if temporary, can damage your sender's reputation. This, in turn, may lead to potential blacklisting, lower inbox placement, and being flagged as spam, reducing your email deliverability and the overall effectiveness of your mailing campaigns.

This can also result in a loss of resources since each bounce implies a misuse of time and money. Specially, for large campaigns. Besides, in the long term, soft bounces affect your metrics, making it more difficult to track your campaign’s performance and to adjust your strategies for better deliverability results.

Hard Bounces 101

On the other hand, a hard bounce occurs when the email address fails to be delivered for a permanent reason. This means delivery will not succeed regardless of adjustments or retries. 

The main causes of hard bounces often include:

• Invalid or non-existing email address. This means that either the address was mistyped, or the address no longer exists. Some case scenarios cover misconfigured or expired email domains, as well as fake and deactivated addresses.
• Permanently blocked domains. Most times, permanent blocking is manually applied by the recipient or their email provider. This can be either because the recipient does not want to receive your messages, or because your address is blacklisted or has a poor sender reputation.
• Spam complaints. Your email address may be blacklisted by Internet Service Providers or ISPs (resulting, thus, in hard bounces) if several users mark your emails as spam. To prevent this, avoid sending emails to recipients without their explicit consent and promptly resolve soft bounce issues. 

Anyway, the general solution is to remove addresses that result in hard bounces from your email list. If you perform any email list hygiene your first step will be to remove all email addresses that hard bounce. 

Using tools to verify that every email on your contact list is valid and regularly cleansing your lists will also help you reduce the risk of hard bounces. 

Furthermore, double opt-in processes are key in ensuring that only engaged users are receiving your emails. When your customer signs up, they must click a link in an email to confirm their subscription. In this way, you have confirmed that their address is valid—they have already replied to your email!

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Email Reputation & Hard Bounce

Hard bounces have a significant impact on your sender reputation score —a measure of the trust that ISPs have in your mailing practices, that is, of how trustworthy your emails are. Sender reputation is determined by spam complaints, engagement level, and, of course, bounce rates.

When judging sender reputation, hard bounces indicate that the list is of low quality since your emails will consistently bounce to invalid or non-existent addresses. This signals that something is wrong with your list management system and that your emails might be malicious or spammy. 

This negatively impacts the reputation score and can lead ISPs to blacklist you as a low-quality sender. Therefore, if the score is low enough the ISPs may hinder your email deliverability, causing your emails to land in spam folders or, in extreme cases, not to be delivered at all.

Soft Bounces vs. Hard Bounces: Key Differences

Let’s see, head to head, how hard and soft bounces compare. More specifically, let’s see where the key differences between them lie, and what this entails.

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Best Practices for Managing Bounces

By now, you know the basics of hard vs. soft bounces and have some notions on why they should be avoided to ensure your email marketing campaigns are successful. However, it is impossible to avoid every little email bounce. 

After all, inboxes fill up, people get on vacations and stop checking their emails, and, spelling mistakes are always on the agenda. Bounces come with the territory of sending email marketing… But we can still take measures to prevent bad data from entering our list in the first place as well as delivery failures.

We have already mentioned some strategies you can apply to reduce bounce risk. Let’s delve further into them. 

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Keeping it Clean

A healthy email list contains, primarily, valid addresses of active, engaged contacts. This proves key when attempting to lead a successful email marketing campaign since: 

• The likelihood of high bounce rates (either hard or soft) will be reduced, preventing its negative effects on your reputation.
• A healthy email list helps you guarantee that your messages will be successfully delivered, as well as opened if the recipient has a high level of engagement.

But mailing health requires a long-term commitment, with constant updates where potentially harmful contacts are removed. Some measures you can take are:

• Ask active subscribers to update their contact information on a regular basis. This helps you avoid including misspelled or outdated addresses on your list. 
• Just in case, regularly scrub your list for common misspellings in email domains. For example, gamil.com instead of gmail.com.
• Remove users who haven’t interacted with your emails for 6-18 months, depending on your email frequency and the type of product or service you offer.
• Email addresses that cause hard bounces from the onset, should be immediately removed to protect your sender's reputation and prevent resource waste.
• Depending on the Email Service Provider you use, soft bounces may turn into hard bounces after a certain threshold is surpassed. 

Segmentation & Personalization

A crucial aspect of managing email bounces (both soft and hard) depends on the engagement of your contacts. Therefore, it’s key to ensure your emails are sent only to interested users who are likely to open them. This has multiple benefits since higher open rates strengthen sender reputation, enhancing email deliverability and making your mailing campaigns more effective overall.

There are different strategies you can implement to craft a highly engaged email list, namely:

• Segmenting your contact list into smaller groups based on various criteria allows you to send content that is specifically relevant to each group. This increases the likelihood of engaging users, reducing bounce risk.
•  Sending personalized content, tailored to appeal to specific recipients. According to the American Marketing Association, such emails are 26% more likely to be opened. To personalize emails, you can include the recipient’s name, preferences, search history within your website, etc.
• Include an opt-out (or “unsubscribe”) option on each email. This ensures that only interested recipients remain subscribed, meaning only people who want to receive your emails will continue to get them.

Email Validation Tools 

Let’s say your organization acquires a new list of customer email addresses, you may have no idea how they were sourced, or if they are valid.  Your email correspondence is too crucial to the company to risk adding unverified addresses to the list. 

Nonetheless, your chance for the double opt-in has passed, and you can’t afford to risk your sender's reputation. What is a man (or woman) to do in such a desperate stance, but to seek a proven means to verify a list of addresses?

The good news is that such a means exists: email validation APIs. These tools take an email address as input and test several criteria about it for validity. Most commonly:

• Syntax. Check that the email address follows the proper format.
• Domain. Ensures the email address uses a valid domain.
• Mailbox. Determines if the specific email address can receive messages.
• Blacklist. Establishes whether the email address or domain is blacklisted.

Addresses that are rated as undeliverable can be pruned from the list… That way, you will know you have protected your email campaign’s sender reputation!

One such email validation API is available from AbstractAPI. Sign up, and you’ll receive a free API key, to easily validate email addresses on your lists.  

Authentication & Compliance

Another practice for successfully managing email bounces is to follow up on authentication protocols and, of course, comply with legal requirements for email marketing campaigns. More specifically, authenticating your email address verifies your identity, preventing email spoofing and enhancing your reputation score.

Most common authentication methods include protocols like:

• DKIM (DomainKeys Identified Mail). By adding a digital signature, this protocol guarantees that your email’s content hasn't been altered during transit. To set up DKIM, create a private/public key par. The public key should be added as a DKIM record to your DNS settings.
• SPF (Sender Policy Framework). This protocol confirms that the server is allowed to send emails on behalf of the domain owner. You can create an SPF record within your domain’s DNS settings. To do so, you will have to list the mail servers authorized to send emails from your domain.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance). It authenticates emails, as well as specifies how messages that fail SPF or DKIM checks should be handled  (e.g., reject, quarantine, or accept them). DMARC records are also created in your DNS settings. 

Make sure you adhere to GDPR (General Data Protection Regulation) when operating within the EU. This involves obtaining explicit consent from your contacts before sending marketing emails. Also, you have to provide an easy way to opt out and, last but not least, protect your contacts’ data.

Compliance with CAN-SPAM (Controlling the Assault of Non-Solicited Pornography and Marketing) is also a requirement when conducting mailing campaigns. Some specific items to observe are:

• Including an opt-out link.
• Using an accurate subject line.
• Providing clear sender information.
• Identifying your emails as marketing content.

Monitoring Bounce Rates

Few email marketing campaigns are truly successful from the onset. Most times, they require adjustments based on specific metrics. Consequently, tracking several rates (particularly bounce ones) is crucial when email marketing is at stake.

So, some metrics you may want to take into account when reviewing your mailing campaigns are:

• Bounce rate (both hard and soft). That is the number of emails that couldn’t be delivered.
• OOO (Out-of-Office) messages. Messages that are successfully delivered, but won’t be read for a certain amount of time. 
• Open rate. How many recipients opened your messages?
• CTR (Click-Through-Rate). The percentage of users that clicked on your email’s links.
• Conversion rate. In other words, the amount of recipients that followed the Call to Action your email proposes.
• Unsubscribe rate. The number of users who choose to opt-out of your list.
• Spam-complaint rate. How many of your emails were flagged as spam.

Industry standards suggest that a healthy email campaign should aim for a bounce rate lower than 2%. Rates above this threshold indicate issues with list quality or sending practices. However, acceptable bounce rates can vary slightly depending on the industry and the type of audience you are targeting. 

For example, in 2023 the average bounce rate across all industries was 1.98%. However, Marketing and Tourism had bounce rates of 3.21% and 2.73%, while Non-profits, Education, and E-commerce had lower rates at 1.20%, 1.35%, and 1.37%, respectively. 

This doesn’t mean that certain industries have better bounce rates, but rather that different sectors engage with their clients differently, making email communication more or less effective depending on the industry. 

In any case, regular monitoring and maintenance of your email list are crucial for staying within these standards since high bounce rates can skew your email marketing analytics, leading to inaccurate engagement metrics. 

More specifically, it affects open rates, click-through rates, and overall campaign performance analysis. Besides, by inflating the number of undeliverable emails, bounce rates make it harder to gauge the true interest and engagement of your audience.

Key to Success: Why is Bounce Management crucial in Email Marketing?

Let’s break down why bounce rates impact sender reputation and email deliverability when they surpass accepted thresholds, making it a crucial factor in every email marketing campaign. Mainly:

• High bounce rates indicate poor list quality. ISPs consider this a sign of negligent or spammy behavior, which lowers your reputation score.
• Anti-spam systems flag your address. High bounce rates trigger spam filters, typically associated with spam campaigns that use unverified email lists.
•  Frequent bounces damage your credibility, to ISPs and recipients. This happens because it shows you are not managing your list adequately. Having your messages land in a spam folder makes it more difficult for the users to trust you as a sender.

All of these factors can lead to blacklisting or emails being redirected to spam folders, affecting deliverability and lowering engagement, open, and conversion rates. Bounce management is, therefore, key to successful email marketing campaigns: maintaining a positive sender reputation will ensure that emails reach the main inbox. 

Proven Bounce Management Strategies

It is fair to ask whether bounce management really affects your mailing success. But, since seeing is believing, let’s briefly review some case studies of email deliverability problems. 

In 2023, Folderly helped full-service artist development agency No Rules PR to increase email deliverability from 15% to 96%. To do so, first, they performed an email deliverability test to assess what was causing such bounce rates. Folderly professionals determined that No Rules PR emails presented several issues. Among them:

• Incorrect SPF and DMARC record settings.
• Spam-triggering words.
• Excessively large messages.
• Usage of HTML templates for cold emails, which caused ESPs to flag them as “promotional” messages.

Folderly optimized those messages to fit email size limits, and corrected SPF and DMARC records. Four months later, No Rules PR started getting consistent results, eventually reaching a deliverability rate of 96%.

A second case study proving the effectiveness of bounce management is that of CLX, a marketing academy that boosted its mailing campaign results by unsubscribing 83.000 email addresses. 

Briefly, this helped them optimize their investment, enhance sender reputation and deliverability, and most importantly, reactivate inactive leads.

Managing Hard Bounces, One Platform at a Time

Email marketing platforms have specific means of handling hard bounces. Understanding the differences between them is crucial for managing hard bounces like a pro. So, ready to dive in?

Mailchimp

This platform automatically distinguishes between soft and hard bounces. Soft bounces can be resend up to 7 times for unsubscribed recipients, and up to 15 for previously active subscribers. After that, they are classified as hard bounces. 

Email addresses that result in hard bounces are immediately removed from your active list to prevent a decrease in your sender reputation and improve future deliverability.

Mailchimp also provides detailed information on which email addresses bounced, as well as on the type of bounce. This further aids in list management and strategy adjustments.

To optimize bounce handling in this platform you can:

• Regularly check bounce reports to identify trends or specific deliverability issues.
• Customize settings for how many soft bounces are acceptable before an address turns into a hard bounce.
• Integrate signup forms to ensure only engaged users remain on your email lists.

SendGrid

SendGrid classifies bounces into hard and soft categories and provides detailed information on their causes. As a user of this platform, you can access this data via the SendGrid dashboard or API. 

To protect your sender reputation, SendGrid adds bounced email addresses to suppression lists and offers real-time notifications about bounce events, enabling immediate action and list updates. 

If you want to enhance your bounce management via SendGrid, we advise you to:

• Ensure bounced email addresses are automatically excluded from mailing campaigns using SendGrid’s suppression list feature. For better results, frequently review this list to ensure data accuracy.
• Perform A/B tests for email content and subject lines. This way, you can avoid formatting issues that may cause soft bounces that, in time, turn into hard bounces.

Constant Contact

This platform provides step-by-step guides to maintain list hygiene, as well as useful advice on managing email bounces and boosting mailing effectiveness. It offers bounce reports with data on each bounce cause, as well as tools to efficiently manage email lists.

Besides, Constant Contact includes automation functions, to instantly remove or flag invalid email addresses, preventing delivery and reputation issues. Some tips to further benefit from this platform are:

• Employ Constant Contact's reporting tools for deeper insights into outdated or disengaged contacts. This will help you determine the appropriate actions to take.
• Craft personalized emails with its automation features, to enhance recipient’s engagement and ensure you only contact permission-based lists.
• Automatically resend emails for soft bounces, in time-sensitive campaigns.

HubSpot

Last but not least, HubSpot also categorizes bounces into hard and soft. Hard bounces are automatically flagged as ineligible for future campaigns, preventing sender reputation issues. Soft bounces are monitored and are treated as hard bounces if an address bounces several times.

This platform provides analytics to monitor bounce rates across different campaigns, helping you to identify patterns and correct mistakes. Also, since it integrates with Abstract, you will be able to verify every address on your list with our API, starting for free!

When using HubSpot, you can enhance your bounce rate management by:

• Incorporating automated workflows to identify and remove hard-bounced email addresses from active lists.
• Manually reviewing contacts that were flagged as “ineligible” because of hard bounces. If they are active, verify their addresses and reactivate them.
•  Personalizing email sending times and content, increasing engagement, and reducing soft bounces likeability. 

Tools & Resources for Bounce Management

Every person who ever watched Mickey Mouse Clubhouse knows how important tools can be. Handling soft and hard bounce is no exception to this. Therefore, let’s briefly review some of the most practical and effective resources for bounce management you can find nowadays.

Validating your Email List

To ensure every email address on your list is able to receive your messages, you can check them on an email validation tool. Some reliable options are:

• Hunter. Its email verification tool allows you to check an address’s syntax, verify its domain, and validate its MX record. It also confirms that an email address exists on publicly available sources, for more confidence. Hunter easily integrates with HubSpot, Zapier, and Salesforce, among other tools.
• Abstract API. This developer-friendly platform offers you real-time email validation. It verifies an address’s syntax, format, domain, and MX record, and features several API keys and test environments. Furthermore, it detects disposable and temporary email addresses, as well as spam traps to prevent long-term deliverability issues. 
• ZeroBounce. As its name indicates, this tool strives to reduce their costumer’s bounce rates to zero. It provides a fast, accurate, and comprehensive email verification service you can test for free on its page. This tool does not only validate email syntax, domain, and server response but also identifies spam traps and rates email addresses’ quality using AI-based scoring.

Leaving Nothing Out: Using Analytics Tools

As we have seen, a crucial aspect of bounce management consists of analyzing metrics. Consequently, you have to make sure that you retrieve the proper information when conducting mailing campaigns. Having the right tools is key to it.

• Mixpanel. This behavioral analytics tool is useful for monitoring real-time email interactions and bounce rates. It allows you to segment users, based on their engagement. Besides, it has a user-friendly interface, easy to implement, and advanced features.
• Piwik PRO. This platform is ideal for tracking how email campaigns impact user behavior, bounce rates, and engagement included. It displays customizable reports and data visualization. Piwik PRO also complies with GDPR to ensure privacy and data protection.

Unbelievers, refrain

To prove to you how useful these tools can be, let’s overview another couple of stories where resources for email bounce management were fundamental to conducting successful email campaigns.

Some time ago, MediaShares agency experienced a severe increase in their bounce rate (it reached 12%), which caused their ESP to cancel their service. By using ZeroBounce, this agency was able to accurately cleanse its contact list, identifying fake and invalid email addresses through ZeroBounce’s verification tool. 

According to this platform’s case study, MediaShares' bounce rate was successfully reduced to 0% after implementing this tool.

For its part, Mixpanel analytic features helped Australian Life Tech gather insights on the success of marketing strategies for 28 By Sam Wood online fitness program. 

Some of the metrics they were able to track include the number of subscribers (active, inactive, new, etc.), the effectiveness of different promotions to encourage sign-ups, and which online behaviors correlate to higher user retention.

All of this was used as a basis for developing more specific, sharp, campaigns that not only reduced the likelihood of email bounces but also fostered conversions.

Conclusion: Better Mailing Practices, for Better Rates

Emails are a way to bridge the gap between users, traveling across the web at minimal cost. However, email bounces often remind us that landing in our (potential) clients’ inboxes isn't as simple as it seems.

Broadly speaking, email bounces can be classified into hard or soft. Hard bounces signal permanent, unsolvable issues, while soft bounces are temporary problems that can typically be resolved after a few retries. 

Nonetheless, both of them limit, more or less directly, your future chances of landing in your customer’s inbox, by affecting your sender's reputation and email deliverability. 

But every cloud has a silver lining. In this case, the good news is that there are several ways to prevent hard and soft bounces. Specifically, a set of best practices that help ESPs and ISPs verify you as a trustworthy sender, ensuring that the recipient actually wants to receive your emails.

Some of them, like validating your email list or monitoring your bounce rates, are better carried on with tools specifically designed for that purpose—like Abstracts API.

Improving your email marketing campaigns has never been easier. Get your API key in a few seconds and start operating with our email validation tool for free. 

Already playing in the big leagues? Explore our integration options to seamlessly connect our services with your existing systems and applications.

Emails build connections—so do we. Get on board with Abstract API. You need nothing but a click 😜.