A hard bounce means that email delivery to a certain recipient has failed permanently. Most of the time, recipients themselves cause hard bounces to happen.

Hard Bounce Causes

  • invalid email addresses;
  • invalid domain names; or
  • the email server of the recipient, by policy, blocks the delivery.

It happens sometimes that subscribers, for personal reasons, do not wish to give out their real email address. So when filling in the form on your website or landing page, they insert a random email address just to pass the procedure requirements. 

However, it may occur that valid email addresses are giving hard bounces, or the subscriber could have unsubscribed by mistake, and this caused a hard bounce. In such cases, the subscriber needs to opt-in once again to be in your subscribers’ list.

In case of a hard bounce, the sender gets an autoresponder email, also called a delivery notification.

With the SendPulse Email Verifier, you can decrease the number of hard bounces. The service checks your mailing list and removes invalid email addresses. As a result, you stay out of the spam folder, increase email deliverability and your sender reputation.


  1. SendGrid states the difference between a hard bounce and soft bounce and offers tips to avoid them.
  2. HubSpot identifies and compares hard bounce and soft bounce.
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