Soft Bounce vs Hard Bounce: What’s the Difference?

Zack Aab

Soft Bounce vs Hard Bounce: What’s the Difference?

A bounce is from an email being rejected by a recipient’s mail server. However, there are several different reasons why your emails could be bouncing. It could range from the recipient’s mailbox being full, to the domain name not existing. So what differentiates them? One is permanent and the other is not. It is highly suggested to pay attention to your bounce logs as your deliverability reputation can be impacted.

The lighter of the two, a soft bounce, is an email that reached the recipient’s mail server but bounced back before it made it to the recipient. Soft bounces could be caused by a recipient’s mailbox being full, the email server being offline or rate-limiting the number of messages it receives, or the message itself being too large. A soft bounce should be retried for up to 72 hours for one campaign, and then suppressed for that campaign. If a contact soft bounces for multiple campaigns, it is best to suppress the email address entirely.

Soft Bounce Causes:

  • Full mailbox
  • Offline or rate-limiting mail server
  • Your message is too large


  • Retry several times, then suppress for that campaign. Retry in the next campaign and if it still doesn’t deliver, stop sending to the contact.

Hard bounces are emails that have been returned to the sender because there has been a permanent failure, which means retrying won’t change the outcome. These will negatively affect your email deliverability. Some of the more common hard bounces are the recipient’s address being invalid, the domain name not existing, or the receiving server blocking delivery from your domain or IP address. Hard bounces can therefore be a result of a poor sending reputation as well as causing a poor reputation if they are sent unchecked.

Hard Bounce Causes:

  • The email address doesn’t exist
  • The domain name doesn’t exist
  • Your recipient’s email server has blocked your emails


  • Immediately stop sending to the contact
  • Analyze the most common bounces to determine the source of the bad addresses

Knowing the difference between a soft bounce and a hard bounce is crucial when trying to put focus on needed email deliverability efforts. A significant percentage of hard bounces is an indicator of an unhealthy list, so pay special attention to those and take action to analyze your list and clean where it’s needed.


For more information on deliverability problems, contact us.

About the Author(s)

Zack Aab

Before learning how to use email, Zack worked in computer repair, blacksmithing, video production, and knot-tying, but not all at once. Zack has his CIPP/US certification, is definitely not a lizard person, and likes normal human things like email and data privacy and basking on sunny rocks. Follow Zack on LinkedIn

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