Soft Bounce vs. Hard Bounce in Email Marketing: How to Manage Delivery Failures

Few things are more frustrating in Email marketing than crafting a carefully planned campaign, only to find out that many of your messages never made it to their intended recipients. In fact, a number of sources point to the fact that across multiple ESPs, even up to 1 in 6 marketing Emails fail to land in inboxes due to various deliverability issues, significantly impacting the success of your campaigns.

One of the most common culprits? Email bounces. Both a soft bounce and a hard bounce can hinder the performance of even your best marketing or transactional Emails. But understanding the difference between these two Email bounce types is crucial if you want to reduce their occurrence, protect your sender reputation, and ultimately improve your Email deliverability.

So, what exactly is the difference between a soft and hard bounce, and how do they affect your Email marketing efforts? In this article, we’ll: 

• Discuss what is Email deliverability and why does it matter?
• Compare hard bounce vs soft bounce.
• Talk about how to lower your Email bounce rate.

Why Email deliverability is critical to marketing success

Before diving into the specifics of Email bounce types, it’s essential to understand the foundation of Email marketing: deliverability. In essence, Email deliverability refers to the ability of your messages – be it marketing Emails or transactional Emails – to successfully land in your recipients’ inboxes, instead of  being blocked or redirected to the spam folder.

Without strong deliverability, even the most perfectly-crafted campaigns will fail to make an impact, as your messages won’t reach their intended audience. Maintaining high Email deliverability not just ensures your messages are seen, but also protects your sender reputation, which Email service providers (ESPs) closely monitor. Poor deliverability can lead to higher bounce rates and, ultimately, damage your ability to run efficient Email campaigns in the future.

Impact of high bounce rates on sender reputation

High bounce rates can have a lasting negative impact on your overall Email deliverability. When your messages consistently fail to arrive – whether due to temporary soft bounces or permanent hard bounces – it signals to internet service providers that your communication may not be trustworthy. As a result, ISPs may start filtering your incoming Emails as spam or even block it entirely.

To protect your reputation and maximize deliverability, it’s crucial to keep an eye on your bounce rates and take action when issues arise. For more detailed strategies to safeguard your deliverability, explore our comprehensive Email deliverability guide.

Understanding the key differences between soft and hard bounces

Even with the best practices for Email deliverability in place, you may still encounter bounces. However, not all of them are created equal. There are two primary Email bounce types: soft bounces and hard bounces. Understanding the difference between these two is essential to maintaining a healthy sender reputation and improving your Email marketing performance.

What is a soft bounce?

⏳ A soft bounce happens when an Email is temporarily undeliverable. This means the message did reach the recipient’s mail server but couldn’t be delivered to the inbox for a temporary reason. Common causes of soft bounces include:

• The recipient’s inbox is full
• The Email server is down or experiencing temporary issues
• The Email message is too large for the recipient’s mailbox

The good news is that soft Email bounces are not permanent failures. In many cases, your Email service provider will attempt to resend the message several times before marking it as undelivered. Since soft bounces are often due to temporary problems, it’s important to monitor them but not be overly alarmed if they occur from time to time.

What is a hard bounce?

🚫 A hard bounce, on the other hand, is a permanent failure. This happens when the Email cannot be delivered due to a more serious issue that can’t be resolved by simply retrying Common causes of hard bounce Emails include:

• The recipient’s Email address is invalid or no longer exists
• The Email domain name of the recipient’s address doesn’t exist
• The message was blocked by the recipient’s Email server due to security or policy restrictions

Hard bounces are more serious because they indicate that the message will never reach its destination. When you encounter a hard bounce, it’s crucial to remove the invalid address from your mailing list immediately. Continuing to send Emails to hard-bouncing addresses can severely impact your sender reputation and, over time, your Email deliverability.

Why understanding the difference matters

Both soft bounces and hard bounces can affect your Email campaigns, but they require different levels of attention and approaches. The former often resolve themselves, but if they stay persistent, it can signal that something needs your scrutiny – think Email size or server issues. The latter, however, demand immediate action, as repeatedly sending Emails to invalid addresses can lead to a higher bounce rate, trigger spam filters, and damage your ability to efficiently deliver marketing and transactional Emails in the future.

In short, knowing the difference between a hard bounce and a soft hard bounce helps you take the right steps to maintain a clean Email list, protect your sender reputation, and ensure your Email marketing efforts succeed.

Potential causes for Email bounces

Knowing what causes Emails to bounce back can help you take proactive steps to mitigate the issue and improve your Email marketing efforts. As mentioned, Email bounces can be classified into two types: soft bounces and hard bounces, each with its own set of causes. Let’s explore the specific issues behind both.

Causes for soft bounces

Soft bounces are caused by relatively brief conditions that prevent your message from being delivered, even though the recipient’s Email address is valid. Some of the most frequent causes include:

1. Full inbox: If the recipient’s inbox is full, there’s no room for new messages, resulting in a soft bounce. This issue typically resolves itself once the inbox is cleared.
2. Email server issues: Occasionally, the recipient’s Email server might be down or experiencing other temporary issues, making it unable to receive messages. Once the server is back up and running again, delivery might succeed on a subsequent attempt.
3. Message size too large: Emails with large attachments or rich media that exceed the recipient’s mailbox size limits can bounce back. Optimizing your message content and downsizing files can help prevent this issue.
4. Greylisting: Some Email servers use greylisting as a security measure, temporarily rejecting a message until the sender retries later. Most servers will eventually accept the Email after verifying its legitimacy.
5. DNS issues: Domain Name System (DNS) problems, such as misconfigured settings or temporary failures, can cause soft bounces. These issues prevent the recipient’s Email server from properly resolving domain names, but they often resolve once the DNS system recovers or is fixed.
6. Email flagged as spam temporarily: Sometimes an Email is flagged as spam due to specific content or sending patterns, leading to a temporary rejection. If the sender retries, the message might be accepted once the filters deem it safe.
7. Connection timeout: In cases where the sending server cannot establish a connection with the recipient’s server in time, the Email will bounce. This can happen due to network congestion or delays, and usually, the server will attempt to resend later.
8. Anti-spam software delaying the Email: Some servers use advanced anti-spam software that temporarily holds or delays Emails while performing in-depth checks. This delay may result in a soft bounce, but the message can be accepted after the scan is complete.
9. Email server maintenance or temporary shutdown: If the recipient’s Email server is undergoing maintenance or has been temporarily shut down for updates, your message won’t be delivered until the server is operational again.

Causes for hard bounces

Hard bounces are more critical, as they indicate permanent Email delivery failure. The most common reasons for hard bounces include:

1. Invalid Email address: If the Email address no longer exists or was entered incorrectly, the message will hard bounce. This could be due to simple typos, outdated contact information, or fake Email addresses altogether.
2. Non-existent domain: If the domain name in the recipient’s Email address is no longer active or was typed incorrectly (e.g., @gnail.com instead of @gmail.com), the message won’t be delivered, and a hard bounce will occur.
3. Blocked by the Email server: The recipient’s Email server might block your communication due to certain restrictions, such as your IP being blacklisted, content being flagged as spam, or the recipient’s server having strict policies against certain types of Emails. This often happens when sending campaigns to outdated or purchased lists.
4. Authentication failures: Some servers will reject Emails that fail authentication checks, such as SPF or DKIM validation. Ensuring that your messages pass these tests is essential for avoiding hard bounces and maintaining good Email deliverability.
5. Email address does not accept mail: Some addresses are set up to receive no messages at all. These addresses might be placeholders or used for specific purposes (like internal systems). Any attempt to send an Email to these addresses will result in a hard bounce.
6. Recipient Email server permanently unavailable: If the recipient’s server has been permanently shut down or is no longer active, your message will hard bounce. This bounce is definitive and signals that delivery is impossible.
7. Policy-based rejections: Some Email servers are configured with strict rules that reject messages based on specific sender policies. For example, certain servers will reject messages from senders that do not meet their internal Email security standards or policies. This leads to a hard bounce since the server will not allow retries.
8. Incorrect MX records: If the recipient’s domain’s Mail Exchange (MX) records are misconfigured or incorrect, the Email cannot be routed to the correct server and will result in a hard bounce. This issue typically requires the domain administrator to resolve.
9. Email address is deactivated or deleted: When a user deactivates or deletes their address, any message aimed at it becomes undeliverable, causing hard bounces. This often occurs when people leave a company or switch to a new provider.

How to reduce your Email bounce rate?

While it’s impossible to completely eliminate instances of undelivered Emails, there are several best practices you can follow to significantly reduce both soft bounces and hard bounces.

1. Regularly clean and update your Email list

One of the most effective ways to reduce bounces is by regularly cleaning your Email list. This involves removing outdated, invalid, or inactive addresses. You can achieve this by:

• Using Email verification tools: Before sending out a campaign, use verification services to check if the addresses on your list are valid and active. This helps prevent hard bounces by catching invalid entries early.
• Removing hard bounces immediately: When a hard bounce occurs, it’s essential to remove that address from your list. Continuing to send Emails to invalid addresses further increases your bounce rate and will hurt your sender reputation.
• Segmenting inactive users: If a recipient hasn’t engaged with your Emails for a long time, consider moving them to a re-engagement campaign or removing them from your main list. Inactive users are more likely to result in soft bounces over time.

2. Ensure proper Email authentication

Proper Email authentication not only helps improve deliverability but also prevents your communication from being blocked or marked as spam, which can cause hard bounces. Make sure your Emails are all in line with the following protocols:

• SPF (Sender Policy Framework): SPF ensures that your Emails are coming from an authorized server. Setting this up properly reduces the likelihood of your messages being blocked by recipient servers.
• DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to your Emails, which helps prove that the message content has not been tampered with. This is essential for passing authentication checks and avoiding deliverability issues.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance): DMARC builds on SPF and DKIM to provide even greater protection, helping to prevent spoofing and phishing attacks. Ensuring your DMARC settings are correct can improve overall deliverability and reduce bounces.

3. Avoid purchased or low-quality Email lists

Using purchased or rented lists may seem like an easy way to scale up your campaigns, but in reality it’s a no-go, often leading to high Email bounce rates. These lists typically contain outdated or fake addresses, leading to undeliverable Emails. Stick to building your own legit opt-in list including people who are genuinely interested in your content and offers. This will lower your bounce rate while improving engagement at the same time.

4. Monitor your sending frequency and volume

Sending too many Emails in a short period can overwhelm recipients and lead to increased soft bounces, especially if inboxes become full. On the other hand, sending too infrequently can lead to hard bounces as Email addresses become inactive over time. To strike the right balance:

• Monitor engagement patterns: Analyze how often your audience prefers to receive Emails and adjust your sending frequency accordingly.
• Gradually ramp up campaigns: When sending to large lists, avoid sending to everyone at once. Instead, send to smaller batches and gradually scale up. This approach helps identify potential issues allowing you to act without affecting your entire list.

5. Pay attention to contents of a bounce message

Emails that are too large or contain attachments that exceed mailbox limits are likely to result in soft bounces. To avoid this:

• Optimize image sizes: Use compressed images and avoid sending Emails with heavy attachments.
• Keep your Email size within reasonable limits: Large, media-heavy Emails can get rejected, so ensure your content design is optimized for fast loading and delivery.

6. Monitor and analyze bounce data

To prevent future bounces, it’s essential to consistently monitor your bounce rates and analyze why these delivery failures are happening. Most Email marketing platforms provide detailed reports on soft and hard bounces, allowing you to:

• Identify patterns: Are certain segments of your list more prone to bouncing? Are there specific domains causing issues?
• Adjust accordingly: Use this data to adjust your sending strategies, clean up problematic parts of your list, and optimize for better future performance.

What to do when you encounter a soft or a hard bounce?

So, a soft or hard Email bounce has occurred – what should you do next? Ignoring bounces can lead to bigger problems down the line, like damaged Email deliverability and a poor sender reputation. Fortunately, there are clear steps you can take to address both types of bounces and reduce their impact on your Email marketing efforts.

Handling soft bounce in Email marketing

A soft bounce indicates a temporary issue, meaning there’s still a chance your message can be delivered at a later time. However, repeated soft bounces can affect your overall deliverability, so it’s important to not leave them unattended. Here’s what to do when you encounter soft bounces:

1. Monitor soft bounce trends
   • If you notice multiple soft bounces from the same recipient over several campaigns, this could indicate a persistent issue like an inactive Email account or a full inbox that isn’t being cleared.
   • Most Email service providers will attempt to resend the message a few times after the first soft bounce, so check whether the Email eventually gets through before taking further action.
2. Remove persistently soft-bouncing Emails
   • After several failed attempts (most providers make 3-5 retries), remove persistently soft-bouncing addresses from your main list. You can either move these contacts to a re-engagement campaign or clean them from your list altogether if the issue continues.
   • By keeping soft bounces in your primary list, you risk driving up your bounce rate unnecessarily.
3. Check Email size and content
   • If the bounce was due to an oversized Email, optimize its content. Reduce large attachments or compress images to make the message more manageable. This can help prevent future soft bounces caused by size limitations.

Handling hard bounces

A hard bounce is a more serious issue that requires immediate action. Since hard bounces are permanent failures, continuing to send Emails to those addresses can damage your sender reputation and lead to more messages being blocked. Here’s how to handle hard bounces:

1. Immediately remove hard-bouncing addresses
   • As soon as you encounter a hard bounce, remove the address from your list. Whether it’s invalid, non-existent, or blocked, you won’t be able to deliver future Emails to that contact. Continuing to send communication to hard-bouncing addresses signals to ISPs that you are not maintaining a clean list, which will harm your deliverability over time.
2. Analyze hard bounce data
   • Most Email marketing platforms provide detailed bounce reports. Use this data to understand why the hard bounce occurred. Was the address typed incorrectly? Is the recipient’s domain blocking your messages? Identifying patterns will allow you to take steps to prevent future hard bounces from similar addresses.
3. Revalidate your Email list
   • Try running your Email list through a verification tool, especially before launching major campaigns. This will help catch invalid addresses or inactive domains, reducing the chances of future hard bounces.
4. Review your sending practices
   • If you’re seeing an unusual number of hard bounces, it could be a sign that your Email list contains a high number of outdated or invalid addresses. Review your list-building methods and make sure that your contacts have opted in to receive your communication. Avoid using purchased or rented lists, which are notorious for containing invalid addresses.

Improving your Email bounce rate overall

In addition to taking action when bounces occur, there are proactive steps you can take to lower your bounce rate and improve overall Email deliverability:

✅ Regular Email list hygiene: Periodically clean and update your list, removing invalid or inactive Email addresses. This helps keep your bounce rate low and ensures that you’re sending to active, engaged recipients only.

✅ Segment your list: Send targeted Emails to smaller, more engaged segments of your list. This can help reduce bounces by ensuring your communication is relevant to the recipients and thus more likely to be delivered successfully.

✅ Monitor Email deliverability: Use analytics tools to track deliverability metrics and identify any recurring bounce patterns. Early detection of deliverability issues can help you take corrective action before they affect your campaign results.

Improve your Email marketing by cutting down on hard bounce and soft bounce

Maintaining a low bounce rate is vital for keeping your Email deliverability high, which in turn safeguards your sender reputation. A good sender reputation is crucial for the long-term success of your Email marketing efforts. Without it, even the best campaigns may fail to reach their audiences.

At MessageFlow, we work directly with international Email Service Providers to create infrastructure that ensures 99% deliverability. We offer tools to manage your bounce rate, and with features designed to support your deliverability goals, you can:

• Validate your Email list: Our system scans addresses for errors or invalid characters, helping you catch problematic entries before sending.
• Monitor bounce types: Our comprehensive campaign reports show both soft bounces and hard bounces, giving you the insights you need to take appropriate action.
• Easily manage hard bounces: With just a single click, you can archive all hard-bounced addresses, preventing them from hurting your future campaigns.