Hard vs Soft Bounces in Email Marketing

What They Mean (and Why You Should Care)

If you’ve ever looked through your email campaign reports and wondered what on earth a “hard bounce” or “soft bounce” actually means, you’re not alone. The terminology sounds more like a mattress comparison than a metric – but understanding it is key to maintaining a healthy sender reputation and improving your overall deliverability.

This article breaks down the difference between hard and soft bounces, what causes them, and what marketers can do to prevent both.

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What is an Email Bounce?

An email bounce occurs when your message can’t be delivered to the recipient’s inbox. Instead, the receiving mail server sends a message back saying, essentially, “No thanks – this one’s not getting through.”

There are two main types of bounces that email platforms like Mailchimp, Klaviyo, or HubSpot report back to you: hard bounces and soft bounces.

The distinction isn’t just technical – it directly affects your sender reputation, your domain authority, and whether future campaigns land in inboxes or spam folders.

Hard Bounces: When the Door is Closed for Good

A hard bounce means your email was permanently rejected. Think of it as posting a letter to an address that no longer exists – it’s coming straight back to you, marked “return to sender.”

Common Causes of Hard Bounces

• Invalid or non-existent email address (e.g. a typo in the address or a fake submission).

• The recipient’s domain name doesn’t exist (for example, the company shut down or changed domains).

• The recipient’s mail server has permanently blocked your messages.

Why Hard Bounces Matter

Hard bounces are a serious issue for deliverability. Too many of them signal to email service providers (ESPs) that you’re not maintaining a clean list – a red flag for potential spam activity.

How to Handle Them

• Immediately remove hard-bounced addresses from your list.

• Use double opt-in forms to reduce invalid signups.

• Regularly clean and verify your email lists using validation tools like ZeroBounce or NeverBounce.

• If a business client changes their domain, ask for updated contact details rather than continuing to email an outdated address.

Soft Bounces: Temporary Delivery Issues

A soft bounce means the email address is valid, but something temporarily stopped it from being delivered. It’s like knocking on a door when the person’s home but they’ve accidentally locked themselves out.

Common Causes of Soft Bounces

• The recipient’s mailbox is full.

• The mail server is temporarily unavailable.

• The email message is too large (often due to attachments or images).

• The recipient’s server flagged the content as suspicious but hasn’t permanently blocked it.

How to Handle Them

• Most email systems will automatically retry sending a few times before giving up.

• If a contact repeatedly soft bounces over multiple campaigns, consider suppressing them.

• Optimise your emails to be lightweight – keep images small and attachments to a minimum.

• Avoid sending multiple large campaigns too quickly, as this can trigger temporary throttling by servers.

The Key Differences Between Hard and Soft Bounces

Here’s a quick reference table to keep it clear:

Why Bounce Rates Matter for Marketers

Your bounce rate (the percentage of emails that couldn’t be delivered) is a vital metric for assessing list health and campaign performance.

High bounce rates can:

• Damage your sender reputation and cause future emails to land in spam.

• Lower your deliverability rates and engagement metrics.

• Get your domain or IP blacklisted by major ISPs.

A healthy bounce rate for most lists is under 2%. Anything consistently above 5% should prompt a thorough clean-up and verification.

Best Practices to Reduce Bounces

• Use confirmed (double) opt-ins: Ensures that subscribers actively validate their address.

• Clean inactive lists: Remove users who haven’t opened an email in 6–12 months.

• Authenticate your emails: Set up SPF, DKIM, and DMARC to verify your sending domain.

• Segment your lists: Avoid sending the same large blast to every contact. Target smaller, relevant groups.

• Monitor feedback loops: Most ESPs provide reports on complaints or deliverability issues – use them.

When a Bounce Isn’t Really a Bounce

Sometimes what looks like a bounce isn’t actually one. For example:

• Auto-replies (like “Out of Office” messages) don’t count as bounces.

• Temporary greylisting (when a mail server delays acceptance to filter spam) can be retried successfully later.

• Suppression lists within your email system may block sends before delivery is even attempted — these aren’t true bounces either.

TL;DR

• Hard bounces = permanent failures. Remove these contacts immediately.

• Soft bounces = temporary issues. Monitor and retry before removing.

• Keep your bounce rate under 2% for good deliverability.

• Clean lists, authenticate domains, and avoid sending bulky emails.

In short: a hard bounce means it’s time to let go; a soft bounce means give it a bit of time. The key is to keep your lists clean, your data accurate, and your emails welcome in the inbox – not the spam folder.