Hard Bounce


A hard bounce is an email term that refers to an email message that has been permanently rejected by the recipient’s email server. This occurs due to invalid email addresses, such as non-existent or deactivated accounts, or when the receiving server explicitly blocks the sender. It is important for email marketers to monitor and manage hard bounces, as they can negatively impact email deliverability and sender reputation.


The phonetics of the keyword “Hard Bounce” are:/ hɑrd baʊns /H – /h/ (as in “house”)A – /ɑ/ (as in “car”)R – /r/ (as in “red”)D – /d/ (as in “dog”)B – /b/ (as in “ball”)O – /aʊ/ (as in “cow”)U – /ʊ/ (as in “put”)N – /n/ (as in “not”)C – /s/ (as in “sink”)E – silent

Key Takeaways

  1. Hard Bounce refers to an email that has been rejected by the recipient’s mail server due to an invalid or non-existent email address.
  2. It is important for email marketers to frequently manage and clean their email lists by removing hard bounce email addresses to maintain a healthy sender reputation.
  3. Hard bounced emails can negatively impact email deliverability and campaign performance, as mail servers and ISPs monitor bounce rates of the sender to maintain inbox quality for their users.


The technology term “Hard Bounce” is important because it represents a crucial aspect of email marketing, campaign management, and maintaining sender reputation.

Hard Bounce indicates a permanent delivery failure of an email due to various reasons, such as an invalid email address, a deactivated recipient account, or a blocked domain.

It is essential for marketers and businesses to track and manage hard bounces carefully, as a high hard bounce rate can lead to a negative impact on the sender’s reputation, email deliverability, and overall campaign performance.

Moreover, ISPs and email providers actively monitor bounce rates to protect their users from spam and malicious messages.

Therefore, optimizing and maintaining a low hard bounce rate is crucial for achieving successful email communications and maintaining positive sender credibility.


Hard bounce is a crucial component in email marketing campaigns that helps maintain a clean and efficient mailing list, while also protecting an organization’s sender reputation. This serves as an indication of the fundamental problems in an email campaign that cannot be solved through simple re-sending attempts. As the term denotes, a hard bounce is an email that is unable to reach its intended recipient due to a permanent issue, such as an invalid email address, a non-existent domain name, or a blocked email server.

Detecting such errors in time saves resources, reduces sending costs, and improves overall deliverability. Furthermore, by removing hard bounces from mailing lists, businesses can better assess the effectiveness of their email campaigns by more accurately measuring engagement rates. Another critical function of hard bounce detection is in preserving a sender’s reputation, a factor that email service providers (ESPs) heavily rely upon for filtering and ensuring the proper delivery of emails.

ESPs typically penalize organizations that continuously send emails to invalid or non-existent addresses, which may lead to their messages being marked as spam or, in extreme cases, being entirely blocked. Hence, adequately managing and addressing hard bounces are essential aspects of email marketing strategies. By monitoring hard bounce rates, businesses can identify issues that affect their email deliverability early on and take corrective measures.

This results in more efficient email campaigns, boosted engagement, and the ability to reach prospects, ultimately driving business growth.

Examples of Hard Bounce

A “hard bounce” refers specifically to email marketing, where an email sent to a recipient fails to be delivered due to a permanent issue. Here are three real-world examples of hard bounce situations:

Non-existent email address: Let’s say a company called FashionCart sends out a promotional newsletter to their subscriber list. One of the email addresses, [email protected], does not exist because it was mistyped during the customer’s sign-up process. When the FashionCart email arrives at the server, the server alerts FashionCart that the [email protected] address is non-existent, resulting in a hard bounce.

Closed email account: Consider a scenario where customer John Smith had subscribed to a weekly blog post update from TechWorld using his email address [email protected]. After a few years, John decides to switch to another email provider and shuts down his account. As a result, when TechWorld sends their weekly blog post update, it gets returned as a hard bounce due to the closed email account.

Domain issues: In another situation, a local bakery sends a monthly newsletter to its subscribers. One of the email addresses included in their list is [email protected], but the entire domain has been taken down due to legal issues. When the bakery sends out their newsletter, the email server returns the message to the bakery as a hard bounce, since the entire domain no longer exists.

FAQ: Hard Bounce

What is a hard bounce?

A hard bounce is an email message that has been returned to the sender due to a permanent error, such as an invalid email address or a non-existent domain. The failure is typically due to the recipient’s email address being incorrect, inactive, or completely invalid.

What causes a hard bounce?

Hard bounces can be caused by various factors, including:

  • Incorrect email address (typos, misspellings, etc.)
  • Domain does not exist
  • Email address has been deactivated or deleted
  • Mail server is blocking the incoming email

How can I prevent hard bounces?

To prevent hard bounces, follow these best practices:

  • Update and maintain a clean email list
  • Use double opt-in methods for subscribers
  • Regularly remove invalid, inactive, or non-existent email addresses
  • Implement real-time email validation on sign-up forms
  • Monitor bounce reports to identify common issues and errors

How do hard bounces affect email deliverability?

Hard bounces negatively impact email deliverability as they can harm the sender’s reputation and overall email deliverability rate. If a sender consistently sends messages to invalid email addresses, internet service providers (ISPs) may perceive the sender as a potential spammer, which can lead to emails being filtered into spam folders or even blocked entirely.

What should I do if I notice a hard bounce?

If you notice a hard bounce, it is crucial to investigate the issue and remove the problematic email address from your list. Investigate the reason for the bounce (i.e., incorrect email address, non-existent domain, etc.), and take the necessary action to prevent further hard bounces. Monitoring your bounce rate and maintaining a clean email list helps maintain a good sender reputation and ensures successful email deliverability.

Related Technology Terms

  • Email Bounce
  • SMTP Error Codes
  • Invalid Email Addresses
  • Email Deliverability
  • Mail Server Rejection

Sources for More Information


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