Hard bounce vs soft bounce: What's the difference?

According to the DMA's Marketer Email Tracker 2026, email remains a core marketing channel, with 74-83% of marketers using it across every stage of the customer journey. Deliverability, however, remains one of the most underestimated threats to the performance of your email marketing performance. Understanding the difference between a hard bounce and a soft bounce is an essential part of effective email deliverability. While both result in an email not reaching its intended recipient, the causes and implications are very different.  

Mailbox providers such as Google and Microsoft consider factors such as the quality of your email list sender reputation and sending practices when determining whether your emails reach a recipient’s inbox. A high number of bounces can have a negative impact on your sender reputation, inbox placement and the overall performance of your email marketing campaigns.  

In this blog, we'll explain the differences between hard and soft bounces, why they matter for deliverability, and practical ways to reduce bounce rates and improve your sender reputation. 

Quick answer: What is the difference between a hard bounce and a soft bounce? 

A hard bounce is a permanent email delivery failure. Reasons for a hard bounce include having an invalid email address, a non-existent domain or a recipient server that has permanently rejected or blocked your email.  

A soft bounce is a temporary email delivery failure. Reasons for a soft bounce include the recipient having a full mailbox, temporary server problems or due to the size of the email. The email address is valid, but the message cannot be delivered at that time. Depending on the reason for the soft bounce, delivery may be successful at a later date.

What is a hard bounce? 

A hard bounce occurs when an email has been permanently rejected and cannot be delivered to the intended recipient. Common reasons for a hard bounce include: 

• The email address is invalid. 

• The email address does not exist. 

• The domain does not exist. 

• The receiving mail server has permanently rejected the message.  

Continuing to send emails to an invalid address can damage your sender reputation and negatively affect deliverability. Suppressing hard-bounced addresses helps protect the reputation of your sending domain and improves the likelihood of future emails within your campaign list reaching inboxes. This is recommended by all the major email service providers and aligns with industry best practices.  

In e-shot, when a hard bounce occurs, it automatically adds the address to a suppression list within your sub-account. This prevents your future campaigns from being sent to an address that is known to be undeliverable, which in turn protects your sender reputation without you needing to do the manual work 

What is a soft bounce? 

Unlike hard bounces, which are permanent, soft bounces are generally temporary and may resolve without any action from the sender. A soft bounce occurs when an email cannot be delivered because of a temporary issue. The email address is valid, and the email has successfully reached the recipient's mail server, but delivery cannot be completed. Common reasons for a soft bounce include: 

• The recipient's mailbox is full. 

• The receiving mail server is temporarily unavailable. 

• The message exceeds size limits. 

• The email has been temporarily flagged by spam filtering systems. 

• Temporary technical issues on the recipient's server.  

In many cases, delivery can be retried successfully once the issue has been resolved. 

Why do email bounces matter? 

Deliverability is becoming increasingly important as mailbox providers use more sophisticated algorithms and AI to determine inbox placement. The DMA's Marketer Email Tracker 2026 found that marketers are becoming more aware of deliverability as a critical success factor, with the report warning that even well-targeted and well-designed emails have little value if they never reach the inbox. 

This means that bounces are more than just a reporting metric. They provide important insights into the health of your email programme. High bounce rates can: 

• Damage your sender reputation. 

• Reduce inbox placement rates. 

• Increase the likelihood of messages being filtered as spam. 

• Impact campaign performance and reporting accuracy. 

• Signal poor data quality to mailbox providers.  

Mailbox providers such as Google and Microsoft  increasingly use sender reputation, engagement signals and technical authentication when determining whether an email reaches the inbox. High hard bounce rates can signal poor data quality and negatively affect future deliverability.  

Understanding the underlying cause of a bounce helps marketers take the right action, whether that's removing invalid addresses, improving list hygiene or investigating deliverability issues. 

What is a good email bounce rate? 

Monitoring your email bounce rate can help identify problems with list quality and deliverability before they impact campaign performance. It is important to note that acceptable bounce rates vary between industries and mailbox providers. Marketers should aim to keep hard bounces as low as possible, guidance suggests hard bounces rates should remain below 5% with many email marketers aiming for rates below 1%.  

It is important to monitor bounce trends over time and investigate any sustained increases in bounce activity. A sudden rise in hard bounces often indicates issues with data quality, acquisition methods or list maintenance. 

4 ways to reduce email bounces 

1. Use an engaged email list 

Regularly spring-clean your database to remove invalid email addresses and monitor inactive subscribers and segmenting audiences based on engagement. Maintaining a clean, engaged email list supports stronger sender reputation and helps improve email deliverability. According to the DMA, 77% of marketers now actively track subscriber activity, recognising that database quality is crucial for long-term deliverability success. 

2. Implement double opt-in 

Double opt-in adds an additional layer of verification to your email subscription process. Subscribers must confirm their email address before being added to your database. Although this approach may result in a smaller list, it helps ensure contacts are genuine, engaged and using valid email addresses. 

3. Monitor your deliverability 

Taking a proactive approach to deliverability can help you identify issues before they impact campaign performance. Using tools such as e-shot's Email Forensics can help to identify potential content, authentication and infrastructure issues before launching a live campaign. 

4. Review campaign reports regularly 

Identifying patterns early can help you address data quality or sending issues before they become more serious problems. Regularly monitoring campaign reports enables you to identify increases in bounce rates and changes in deliverability performance. 

How email validation helps 

Email validation is one of the most effective ways to reduce hard bounces. This process takes place before you send out an email campaign and allows you to assess whether an email address is likely to be deliverable. This in turn can help you to reduce bounce rates and improve overall deliverability. At e-shot, we can help you maintain data quality through our email validation health check. The validation process checks whether an email address: 

• Is correctly formatted. 

• Exists. 

• Uses a valid domain. 

Final thoughts 

Achieving strong email deliverability requires a combination of good data management, effective sending practices and ongoing monitoring. 

Understanding the difference between hard and soft bounces is a crucial first step. By maintaining a clean database, implementing double opt-in, monitoring deliverability and validating your email data, you can reduce bounce rates, protect your sender reputation and maximise the success of your email marketing campaigns.  

At e-shot, our account managers, Forensics platform and email validation services can help you identify and resolve deliverability issues before they affect your results. 

Frequently asked questions (FAQ) for hard bounces and soft bounces 

What causes a hard bounce? 

Hard bounces are typically caused by invalid email addresses, non-existent domains or permanent delivery rejections by the receiving server.  

What causes a soft bounce? 

Soft bounces occur because of temporary issues such as full mailboxes, server outages, message size restrictions or temporary spam filtering.  

Does a soft bounce affect sender reputation? 

A small number of soft bounces is normal. However, repeated soft bounces can affect sender reputation if they continue over time and are not managed appropriately. 

Can a soft bounce become a hard bounce? 

Yes. Some email providers and email service platforms may eventually classify repeatedly soft-bouncing addresses as undeliverable if delivery continues to fail over time.  

How can I reduce hard bounces? 

Yes. You can reduce hard bounces by validating email addresses, implementing double opt-in, removing inactive contacts and maintaining good list hygiene practices. 

Should hard-bounced email addresses be removed? 

Yes. Hard-bounced addresses should be removed or suppressed to protect sender reputation and maintain healthy deliverability rates.  

Last updated: August 2026