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Soft Bounce vs Hard Bounce: Understanding Email Bounces

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Pierre-Yves Dubreucq
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When sending emails via an API or SMTP, you will inevitably encounter bounces. Understanding the difference between a soft bounce and a hard bounce is essential for optimizing deliverability and improving your sending rates.

In this article, we will explain the distinction between these two types of bounces, their causes, and how to manage them effectively.

1. What is an Email Bounce?

A bounce occurs when an email cannot be delivered to its recipient and is returned to the sender with an error message. There are two main types of bounces: soft bounce and hard bounce.

2. Hard Bounce: A Permanently Rejected Email

A hard bounce is a permanent rejection of an email. This means that the email address is invalid or does not exist.

📌 Main Causes:

  • The email address does not exist (e.g., typo or deleted account).
  • The recipient’s domain is invalid or inactive.
  • The receiving server permanently rejects emails from your domain/IP.

✅ How to Handle Hard Bounces?

  • Immediately remove these addresses from your list to avoid reputation issues.
  • Validate your email lists using verification tools before sending.
  • Monitor your hard bounce rate (anything over 1% or even lower can negatively impact your deliverability).

3. Soft Bounce: A Temporarily Undelivered Email

A soft bounce is a temporary rejection. The email might be accepted later after multiple attempts.

📌 Main Causes:

  • The recipient’s mailbox is full.
  • The recipient’s server is temporarily unavailable.
  • The email is too large and exceeds the server’s size limits.

✅ How to Handle Soft Bounces?

  • Retry sending after a reasonable delay (most systems handle this automatically).
  • If an address generates multiple consecutive soft bounces, consider unsubscribing it.
  • Ensure your emails follow best practices (appropriate size, correct formatting, etc.).

4. Why is Bounce Management Essential?

Ignoring bounces can negatively impact your sender reputation and email deliverability rates. A proactive approach helps you:

  • Maintain a clean and updated email database.
  • Improve engagement rates (fewer emails sent to invalid addresses).
  • Reduce the risk of being blacklisted by ISPs and email providers.

🔥 Best Practices:

  • Set up a webhook to track bounces in real-time.
  • Use a service that automatically removes invalid addresses.
  • Analyze your bounce reports regularly to detect patterns and adjust your strategy.

Conclusion

Understanding the difference between soft bounces and hard bounces is crucial for any developer or email marketer. By implementing effective bounce management, you can optimize your deliverability and improve your campaign performance.

If you’re looking for a unified API for email sending and bounce management, Sweego helps you automate bounce handling and ensure better deliverability. 🚀