Hard bounce vs soft bounce: What every email marketer needs to know in 2025

If you’re serious about email deliverability, you need to know the difference between hard and soft bounces. A hard bounce? That’s a dead end such as an invalid email address, gone for good. A soft bounce? It’s a temporary block, like a full inbox. 

Both can drag down your sender reputation and wreck your inbox placement over time. In this article, we will focus on the causes of these bounces, why they matter, and how to handle them in 2025.

What are email bounces and why are they important in 2025? 

Email bounces happen when your email can’t reach its intended recipient and gets sent back. These bounces come in two forms: soft bounces and hard bounces. 

A soft bounce is temporary, maybe the recipient’s inbox is full, or their server is down. A hard bounce, on the other hand, is a permanent block, often due to an invalid email address or non-existent domain.

Why does this matter in 2025? It’s simple: bounces impact your sender reputation and in turn, your email deliverability. It means that high bounce rates signal to email providers that your list may be outdated or poorly managed, which can send more of your emails to spam, even for recipients who actually want to hear from you. This is why you need to monitor and manage these bounces to keep your emails visible and effective, bounces being one of the most common email deliverability issues you may face. And that you will face

According to Mailchimp’s data, average soft bounce rates range from 0.34% to 2.82%, while hard bounces fall between 0.33% and 2.62%.

Our tip: you can use tools like Mailreach’s Email Warm-Up and Spam Test to build a strong sender reputation, reduce bounces, and boost the chances of landing in the inbox. 

What is a hard bounce vs. a soft bounce?

A hard bounce means a permanent delivery failure: your email can’t be delivered because the address is either invalid, non-existent, or blocked. Once a hard bounce occurs, there’s no retrying, and that email address should be removed from your list immediately. 

Good to know: Persistent hard bounces damage your sender reputation by signaling to email providers that your list might be outdated or low quality, so be cautious!

On the opposite, a soft bounce is a temporary issue. It means that your email reaches the recipient's server but can’t be delivered, often because the inbox is full, the server is down, or the message is too large. 

In practice, soft bounces may resolve on their own, because email providers typically retry delivery a few times before marking it as failed. But it doesn’t mean that you don’t need to take care of them. Why? Simply because too many soft bounces over time can lead to deliverability issues.

Here’s a quick comparison to clarify:

As you may understand it: while some causes of bounces are straightforward, others indicate deeper issues. For instance, if you see a “550 Permanent Failure” error, it may mean the email address doesn’t exist. 

Learn more on this here: How to Fix 550 Permanent Failure 

Or, if you encounter “550 High Probability of Spam”, it points to a reputation issue, suggesting that your sender reputation may need work. 

Also learn more: 550 High Probability of Spam - Gmail

Common reasons for hard and soft bounces

Common reasons for a hard bounce

A hard bounce occurs when an email can’t be delivered due to a permanent issue. This usually means there’s no point in retrying, and the email address should be removed from your list to avoid further harm to your sender reputation. 

Here are the most common causes of hard bounces:

• Invalid email address: The email address might contain typos or formatting errors that make it undeliverable.
• Non-existent domain: The domain name in the email address doesn’t exist or is spelled incorrectly, making it unreachable by any mail server.
• Blocked address or domain: Sometimes, an email address or domain has blocked messages from your IP or domain, preventing delivery altogether.

Of course, continuing to send to undeliverable addresses will only increase your bounce rate, signaling to email providers that your list may be outdated or poorly managed. So if you’re encountering errors like “550 Permanent Failure” or “550 High Probability of Spam,” these are huge red flags for potential list quality or reputation issues.

Common reasons for a soft bounce

Soft bounces are usually due to temporary issues that may resolve themselves. Email providers will even often attempt to resend the message a few times before marking it as failed. 

Knowing this, let’s focus on the most common reasons for soft bounces:

• Recipient’s inbox is full: If the mailbox is full, the server will temporarily reject incoming messages. This is extremely common when recipients don’t regularly check or clean their inbox.
• Temporary server issues: If the recipient’s server is down or experiencing issues, the email will bounce temporarily until the server is back online.
• Message is too large: If your email includes heavy attachments or large images, it might exceed the recipient’s server size limits and be rejected.

While soft bounces may clear up on their own, it’s important to keep an eye on repeated soft bounces from the same addresses. If the issue persists, it could signal that the address is inactive or has ongoing server problems. And this can be extremely frustrating, and bad for your sender reputation. 

Our solution: use tools like Mailreach’s Email Warm-Up and Spam Test to easily build your sender reputation and improve your chances of consistently landing in the inbox!

How to handle hard bounces vs soft bounces ?

The first thing to know is that each type of bounce requires a different approach to keep your campaigns on track and your emails reaching the right inboxes.

For example, for hard bounces, the best approach is simple: remove these addresses from your list. A hard bounce indicates a permanent issue, such as an invalid email address or a non-existent domain, so continuing to send emails to these addresses will only increase your bounce rate and damage your sender reputation. So to minimize the risk of hard bounces from the start, you can start by using a reliable email verifier like Verifalia or Zerobounce to clean up your list.

Another practical tip is to control the percentage of catch-all emails on your list. Catch-all domains accept all emails regardless of whether the address is valid, which can lead to high bounce rates if many of these addresses turn out to be inactive or fake. We recommend you to also monitor the proportion of catch-all emails in your list and verify them regularly, in order to avoid any surprises.

Regarding soft bounces: should you remove them from your list? Not immediately. Soft bounces may resolve on their own, and in many cases, the email will be delivered after a retry. But if you notice repeated soft bounces from the same address over multiple campaigns, it’s time to consider removing it, as this signals a persistent issue. 

Impact of bounces on sender reputation and deliverability

Bounces directly impact your sender reputation, which is the backbone of email deliverability. In fact, every bounce sends a signal to email providers about the quality of your list and the reliability of your email practices. 

Hard bounces are especially damaging, as they indicate a permanent issue like an invalid address. Too many hard bounces show email providers that your list is poorly maintained, which can quickly downgrade your sender reputation. Over time, this leads to more of your emails landing in spam folders or being blocked altogether.

Soft bounces, while less severe, can also add up if they’re not managed, especially if they’re repeated.

This is exactly why a strong sender reputation remains essential for any email campaign to succeed. Without it, even the best-crafted emails and valuable content won’t reach your audience. 

Keep in mind that managing bounces and maintaining a healthy sender reputation are non-negotiable for effective email marketing!

Best practices for reducing email bounces

Here’s a practical guide to reducing both hard and soft bounces in your campaigns this year:

• 1 - Use an email verifier. Run your list through a trusted email verifier like Verifalia or Zerobounce every 3 months max. These tools can easily identify invalid or inactive addresses, keeping your list up-to-date and helping you avoid unnecessary bounces.
• 2 - Control the percentage of catch-all emails. Catch-all addresses accept emails for any user at a domain, which sounds great until you find that many bounce back. But you must keep an eye on the percentage of catch-all emails in your list, because too many can hurt deliverability. Aim for 20% max. Avoid sending campaigns only to catch-all emails as it will skyrocket your bounce rate. 
• 3 - Use double opt-in to confirm valid addresses (for non B2B emailing). Double opt-in requires users to confirm their email address by clicking a link, reducing the risk of fake or mistyped addresses. Even if it’s a simple step, you will be surprised by how well it ensures your list is full of valid, engaged contacts, reducing hard bounces right from the start.
• 4 - Warm up your sender reputation for B2B cold outreach. If you’re doing B2B cold outreach, use an email warm-up service like Mailreach to have way better chances of generating positive engagement with your emails, making email providers more likely to deliver your messages to the inbox (while knowing the difference between automated vs manual warmup).
• 5 - Test deliverability before sending campaigns. Final advice: run a spam test! Always! Thanks to this test, you will see where your emails are landing before launching your campaign. This helps you identify any issues that could lead to bounces, giving you a chance to adjust before sending.

So here are some key takeaways: minimizing bounces is all about list quality and proactive testing. Start with a clean list, confirm addresses with double opt-in, and use email verification to keep your database accurate. If you’re doing cold outreach, warm up your sender reputation and check your deliverability before sending. For anyone serious about reducing bounces and boosting deliverability, Mailreach’s Email Warm-Up and Spam Test services are the tools you need to maximize success. Try them today to keep your emails on track and landing where they should: in the inbox!