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Hard bounce vs soft bounce: What is the difference?

Reading Time: 9 minutes

Hard bounce and soft bounce: these two troublemakers can spoil not only your email campaign performance, but your sender reputation as well.

Contrary to what many marketers believe, there are different reasons why emails bounce. An invalid recipient’s address, a full mailbox, or DNS issues are the three major reasons email bounce. 

In this article, we’ll discuss hard bounces and soft bounces, and how to differentiate between the two.  

To learn more about email bounce, read “Understanding email bounce: Definition, reasons and best practices.”

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What is a soft bounce?

A soft bounce is an undelivered email message caused by a temporary problem. It means your recipient’s email is valid, and your email message reached the recipient’s mail server. The challenge is that the mail server may have rejected it for several reasons.

In such situations, the mail server will bounce the email back to you with a message that looks like this:

Hard bounce vs soft bounce: Soft bounce example
Image via AcyMailing

Since the recipient’s email is valid, your email may get delivered later. Most times, your mail server will make further attempts to try and deliver the message.

If you’re patient enough, your message may eventually go through. Other times, you may have to resend the email yourself before it goes through.

Temporary server outages, full mailboxes, content filtering, or excessive email attachments are a few reasons for a soft bounce.

Before we take a look at hard bounces, let’s discuss the reasons for a soft bounce in detail.

Mailbox is full

If your recipient’s email inbox has reached its storage limit, all incoming mail will softly bounce back. When this happens, you might get a response like this:

Recipient inbox full sample
Image via

To fix this, your recipient needs to create space in their inbox by deleting old emails. Your email will bounce back if your recipient fails to declutter their inbox.

How can you fix this?

Don’t try to resend the email immediately when you experience a soft bounce like this. Wait for a few hours or days to give the recipient time to declutter their inbox.

Server issues

Like other digital systems, an email server can experience downtime. During this outage, your emails will bounce back. Poor connectivity and other network issues often cause emails to bounce too.

Depending on your mail server, you might get the notification below:

Hard bounce vs soft bounce: Email server outage message
Image via SnapComms

Mail server outages are often planned and may not be an abrupt occurrence. Your mail server should notify you of a scheduled outage so you can plan ahead.

How can you fix this?

  • Email server outages are only temporary, so you can try sending the email again after a few hours.

Email content issues

Sometimes, the content of your email message could lead to a soft bounce. The recipient could have a content filtering system that labels your email as spam or poor quality.

Your email can also soft bounce when you send large attachments that exceed the recipient’s accepted file size.

How can you fix this?

  • Carry out A/B testing. You can also tweak the content of your message to remove any words that the server might flag as spam.
  • Pare down images, GIFs, and any dynamic media. This helps to create a lighter, more focused email.

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    DNS issues

    DNS failure (domain name system) also prevents the recipient’s email server from delivering your message. A DNS failure can cause a soft bounce or a hard bounce, depending on the nature of the problem.

    When DNS servers crash or go offline, they can cause your emails to soft bounce. Servers often resolve DNS issues quickly, but the time frame varies from server to server.

    There’s not much you can do to fix this issue other than wait a few hours or days before trying to send another email. If it’s a temporary DNS issue, your mail should go through within a day or two.

    What is a hard bounce?

    A hard bounce in email marketing usually indicates a permanent error.

    What’s the difference between a hard bounce vs soft bounce? A hard bounce email will not deliver, and your mail server will not make further attempts to deliver the message.

    An unknown user error can cause an email to hard bounce. An unknown error occurs when the recipient’s email address is invalid.

    There are several reasons why the server tags the recipient’s email address as invalid, including:

    • A deactivated email address no longer exists.
    • A typo in the address spelling.

    A hard bounce could also occur when the recipient permanently blocks your emails. Your recipient could have a strict email security filter that prevents your emails from ever reaching them.

    A hard bounce email can spoil your email deliverability and sender reputation. People may treat you as a fraudulent email sender. So, you must avoid a hard bounce as much as you can.

    When your email gets a hard bounce, your mail server often sends a report stating possible reasons for the rejection. Most mail servers use various codes to state different causes of a hard bounce.

    For example, the image below is a mail server’s message stating the reason for a hard bounce:

    Hard bounce example
    Image via VerifyBee

    Let’s discuss in detail the possible causes of those annoying hard bounce emails.

    Invalid email address

    An invalid email address is one of the most common reasons you’re experiencing a hard bounce. Getting even one letter wrong will be problematic.

    The server can also flag the recipient’s email address as invalid or nonexistent when they deactivate their accounts, such as an employee leaving a company. When this happens, you’ll get a message like this:

    Invalid email address example
    Image via 

    How can you fix this?

    • Double-check the spelling to remove typos and unnecessary spacing.
    • Eliminate non-respondent email addresses from your list.
    • Implement double opt-in during subscriber signup to ensure subscribers provide accurate email addresses.

    Domain name issues

    If the domain name on the recipient’s email address is misspelled, the server can flag it as spam or nonexistent.

    When this happens, your mail server may send you the below notification:

    Mail doesn't exist hard bounce email example
    Image via Enginemailer

    How can you fix this?

    • Skim your contacts and check for simple mistypes like, @yahoo.con, etc.
    • Use email verification to ensure email grammar and validation.

    Recipient’s Email Server Block

    Sometimes, your email may not be delivered because the recipient’s email server has put your email address on a blacklist. It could also be blocked when the ESP misidentifies your email as spam.

    If you send large amounts of messages using free email services like Gmail or Yahoo, your email may become a hard bounce.

    The new policies require businesses to use emails with their private business domain ([email protected]). If you don’t comply, your email may not pass authentication and will bounce.

    How can you fix this?

    • Use a legitimate business domain name.
    • Improve your sender reputation by asking recipients to mark your emails as “not spam.”
    • Contact support at the ESP for further assistance.

    Mailbox deactivated or unknown

    Sometimes, a hard bounce can occur for reasons other than a misspelled email address or domain name. The email address may have been valid initially, but the user deactivated or abandoned it.  

    When this happens, the recipient’s mail server is deemed permanently unreachable. In this case, your email will bounce back because it has nowhere else to go.

    How can you fix this?

    • Never purchase or rent email lists. These lists often include old, inactive, and spam trap email addresses that cause high bounce rates.
    • Your subscribers have probably changed their emails, forgotten about you, or are no longer interested in your content. In this case, you should delete users who have been inactive for months.

    What is a hard bounce vs soft bounce in email marketing?

    From an email marketing perspective, the causes of hard bounce and soft bounce are different. The resulting repercussions are different too.

    Let’s discuss the repercussions of a soft bounce:

    • Poor email deliverability: Consistent soft bounces reduce email deliverability.
    • Communication lapses: Important messages may not get to recipients in time.
    • Leads to a hard bounce: Multiple soft bounces become hard bounces, significantly harming your email credibility.

    Repercussions of a hard bounce: 

    • Bad sender reputation: A hard bounce can result in recipients tagging your account as spam. A spam account ruins the sender’s reputation.
    • Low engagement: Your recipients will not engage with your emails if your email is a hard bounce. This is because they never got them in the first place.
    • Wasted resources: A hard bounce wastes time and resources spent on email marketing strategies.

    How to avoid soft and hard bounces

    A high email bounce rate negatively affects your email marketing strategies.

    Not to worry, we’re here to help!

    In this section, we’ll discuss general tips for avoiding soft and hard bounces. It’s always better to avoid soft bounces before they become hard bounces.

    1. Email list cleaning: With time, some subscribers might change their email addresses or stop engaging with your content. When this happens, it may be time to clean up your email list and let them go.

      Send a reactivation or re-engagement campaign to segment contacts who don’t respond. Keep your email list up-to-date. Delete unengaged contacts and work towards getting more active subscribers.

    2. Avoid free sender domains: Ecommerce businesses often send emails regularly. However, it’s recommended to avoid sending business emails from free email services like Gmail or Yahoo.

      Spammers can easily get hold of free sender domains, and recipients can tag you as one of them. Instead, opt for a personalized domain with your business name. This makes you appear professional and legitimate, and increases trust.

    3. Stay in touch with your subscribers: In the ecommerce world, out of sight is out of mind. As such, you must regularly contact your subscribers to remain relevant.

      Reach out to them as soon as they subscribe to your mailing list, but do not overwhelm them with too many emails. Only send messages regularly enough to keep their eyes on you.

    4. Track your email deliverability: Keeping a record is the only way to know how your emails are faring. Use a reliable ESP to track bounce rates and subscriber engagement.

    5. Comply with email regulations: Understand and comply with email laws and regulations. For example, CAN-SPAM, CASL, and GDPR. These laws govern digital marketers’ operations, and violating them might get you blacklisted.

    How can Omnisend help?

    This hard bounce vs soft bounce guide helps you identify the kind of email bounce you’re experiencing and how to rectify it. However, your email marketing strategies are only as good as the ESP you use.

    Omnisend can help you deal with hard bounce vs soft bounce issues or avoid them altogether.

    Let’s look at how.

    Avoid email bounces

    Omnisend can save you the trouble of rectifying email bounces in the following ways:

    • Providing tools to help you with email list cleaning. It automatically removes invalid addresses from your list.
    • Segmenting your audience. It helps you send personalized emails to engage  subscribers and enhance email deliverability.
    • Using message delivery failed automation. It helps you unsubscribe hard bounce email addresses and improve your bounce rate.

    Deal with email bounces

    There are times when you can’t avoid a hard or soft bounce, and you have to resolve the issue. Omnisend can make a hard or soft bounce a walk in the park for you.

     Omnisend helps in the following ways:

    • Providing detailed insights on hard bounce vs soft bounce rates and deliverability. This helps you monitor your performance.
    • Automatically resends soft bounce emails, which increases email deliverability.
    • Designs well-optimized emails to help you avoid bounced emails due to formatting issues.

    General management

    Omnisend manages hard bounce and soft bounce issues. However, the platform also manages other aspects of your email marketing.

    • It integrates with Argoid products, CRM systems, and other ecommerce tools to help you keep a healthy email list.
    • It helps you build a good sender reputation by complying with the necessary email laws.
    • Provides a reliable customer support system to help you with any email bounce issues at any time.

    Key takeaways

    High hard bounce rates negatively impact the sender’s reputation and email deliverability rate. However, even soft bounces might also be a challenge in the long run.

    Regardless of the nature of your email bounce, strive to keep your bounce rate under 2%. The lower it is, the better. Use this professional guide to differentiate between a hard bounce vs soft bounce.

    Our guide will help you plan more effective email marketing strategies. You can also use email best practices to build your list.

    Let uninterested contacts freely unsubscribe. Focus on quality, not quantity. Finally, check and clean your list regularly to avoid issues.

    Start using Omnisend today! Create email campaigns with exceptional conversion rates.
    Article by
    Karolina Petraškienė

    Karolina is a writer, content marketer, and email enthusiast at Omnisend. When she's not curating articles, you can find her in the woods challenging herself in hiking boots or off-roading her bike.

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