Bounced emails hurt your sender reputation and keep your messages from reaching your audience. So what exactly is a bounced email, and how do you fix it? In this complete guide, we’ll check together the types of email bounces, why they happen, and especially how to tackle them. Fast.
What does it mean if an email is bounced ?
A bounced email is one that couldn’t reach the recipient’s inbox. It’s like a package that gets returned to the sender. When an email bounces, it means something along the delivery path went wrong, and your message couldn’t make it through. The most common causes? Invalid or non-existent addresses, full inboxes, and server issues.
Here’s how it works: when you hit “send,” your email provider tries to connect with the recipient’s server to deliver your message. If that server detects an issue—like an address that doesn’t exist or a mailbox that’s full—it rejects the email and “bounces” it back.
Yes, some errors are temporary (like a full inbox), and your email provider may retry sending. But keep in mind that others, like an invalid address, mean that email will never make it through. And that’s bad.
Bounced emails aren’t just an inconvenience; they can drag down your sender reputation if you’re not managing them. Why? Because email providers view frequent bounces as a sign of poor list quality, making it harder for your messages to land in inboxes in the future. So if your emails are bouncing, it’s not just a technical glitch: it’s a huge red flag that something in your sending process needs attention.
Types of email bounces
Email bounces come in two main types: hard bounces and soft bounces.
A hard bounce means the email couldn’t be delivered due to a permanent issue. Think of it as hitting a dead end. Common causes include invalid email addresses (typos or non-existent accounts) and blocked domains. For example, if you’re sending to an email that doesn’t exist or was typed incorrectly, that’s a hard bounce. This type of bounce requires immediate action—remove these addresses from your list to avoid hurting your sender reputation. If you’ve received a “550 Permanent Failure” error, it likely signals a hard bounce.
Learn more on fixing 550 Permanent Failure errors here.
A soft bounce, on the other hand, is a temporary issue that may resolve itself. Your email reached the recipient’s server but couldn’t be delivered to the inbox. Common causes include a mailbox full or temporary server problems. For example, if your recipient’s inbox is overflowing, your email might bounce back until space is freed up. Soft bounces often don’t require immediate removal from your list, but keep an eye on them—repeated soft bounces may indicate an inactive account.
How do you say an email bounced back? Simply put, if an email “bounced back,” it means it couldn’t be delivered and was returned to the sender due to a delivery issue.
For more details on handling hard and soft bounces, check out our full guide: Hard bounce vs soft bounce: what every email marketer needs to know in 2025. And if you’re dealing with issues like “550 High Probability of Spam” or “Access Denied,” these often point to reputation problems that can be addressed with an email warm-up.
Learn more here: 550 High Probability of Spam - Gmail or How to fix “Access Denied - Bad Outbound Sender”.
Causes of bounced emails
When an email bounces, it means the message couldn’t be delivered, and understanding why is key to keeping your email deliverability strong. It’s as simple as that.
Here are the most common causes, and why they matter:
- Non-existent address: One of the main reasons emails bounce is because the recipient's email address doesn’t exist, which often happens when there’s a typo in the address or if the user has deleted their account. So please, remove invalid addresses from your list if you really want to avoid further bounces and maintain a good sender reputation.
- Full inbox: If the recipient’s mailbox is full, their server will temporarily reject incoming messages until there’s room. This is a soft bounce, as it’s a temporary issue that may resolve on its own. But if the inbox remains full over time, it may be worth removing the address from your list if bounces persist.
- Temporary server issues: Yes, sometimes, the receiving email server is down or experiencing temporary issues, leading to a bounce. In these cases, the server may attempt to deliver the message again later. Even if the cause of soft bounces is usually beyond your control, they should be monitored. Especially if it happens frequently with the same address!
- Bad DNS configurations: Your DNS settings (like SPF, DKIM, and DMARC) remain absolutely essential for email authentication. Your priority must be to keep them correctly configured, as the receiving server may reject your email, seeing it as potentially fraudulent or spammy. And yes, this type of rejection directly impacts your email deliverability, as it indicates to email providers that your messages may not be trustworthy.
- Content or reputation-related issues: In some cases, emails bounce because of the content itself or a poor sender reputation. And as a result, spam filters are highly triggered. Let’s take an example: if your emails frequently include phrases or links that look spammy, or if your domain has a reputation issue, the receiving server might block your emails. So use an email warm-up service, such as Mailreach, to quickly improve your sender reputation, especially if you’re engaged in B2B cold outreach. You’re welcome.
Where do email bounces go? Well, bounced emails generate a “bounce-back” message that returns to your inbox or a specified return-path address, providing an error code and brief explanation of why the email wasn’t delivered.
How do I fix a bounced email?
Once an email has bounced, it’s bounced. There’s no way to fix that specific instance. Instead, the real fix is preventing future bounces by reducing your bounce risk.
Here are some tips to minimize bounces in your email campaigns:
- Verify your email addresses: Before even sending email campaigns, make sure your list is clean. Use a trusted email verification tool to check for invalid or non-existent addresses. Removing these right from the start lowers your email bounce rate significantly and improves your sender reputation.
- Monitor your sender reputation: A low reputation can cause bounces. Make sure to monitor sender reputation to ensure they’re in good standing with email providers. You can use Google Postmaster Tools and if you’re sending B2B emails, use MailReach’s email warmup tool.
- Especially avoid spam triggers: Sometimes, bounces happen because your emails get flagged as spam. To avoid this, keep your content clean, avoid spammy phrases, suspicious links, or overly promotional language.
- Retry sending: It may seem simple, but yes, if a message bounces due to a temporary issue, like a full inbox or server problem, do not hesitate to try again after a short delay.
Taking proactive steps to prevent bounces is the most effective strategy. Focus on list hygiene, content quality, and building a strong sender reputation. That’s it.
Monitoring and preventing email bounces
Here’s a clear strategy to monitor and prevent bounces effectively.
- Use an email verifier: Before every campaign, verify your email list. Tools like Verifalia or Zerobounce check for invalid or non-existent email addresses, significantly reducing the risk of hard bounces. Make verification a regular part of your process to keep your list clean and reliable.
- Control the percentage of catch-all emails: Catch-all addresses accept emails sent to any address within a domain but don’t guarantee delivery. High percentages of catch-all emails can lead to more bounces, as they often mask inactive or invalid addresses. Regularly monitor your list for catch-all domains and make sure they don’t represent more than 25% of your contact list. (For more on managing catch-all emails, see our video here: Managing Catch-All Emails).
- Warm up your email account: If you’re doing B2B cold outreach or using a new email address, a warmup is essential. Warming up your account with MailReach builds a positive sender reputation by generating authentic interactions, like opens and replies, which email providers love to see. For those just starting with cold outreach or looking to boost deliverability, MailReach’s email warmup tool is a powerful solution.
Do not forget to run regular spam tests: Spam filters can block emails and lead to bounces if they detect anything suspicious. To stay ahead, you really need to run a spam test to see how your emails are being treated across different email providers. and you’re at the right place: MailReach’s spam test service helps you identify issues and adjust your content or settings before sending a full campaign.
Email Warmup
