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What is the difference between hard and soft bounces?

An email bounce occurs when an email cannot be delivered to a subscriber’s inbox. Bounces are classified as hard or soft bounces. 

A hard bounce is logged when there is an attempt to deliver an email message but the delivery is rejected due to a permanent error, such as an invalid email address. The most common cause of email bounces is a typo in the email address such as:

  • name@gmailcom
  • name@gmail,com
  • name@gmail.con

A soft bounce is logged when an email is sent, processed by the subscriber’s server and then the message is returned to LibraryAware.  Soft bounces may occur if the subscriber’s server is not available or if the subscriber’s mailbox is over its size limit.  

LibraryAware will only attempt to deliver an email publication once to a particular email address. If a soft bounce occurs, that email will not be resent.  

When emails to a particular email address soft bounce five times, those soft bounces will be converted and logged as a hard bounce. When an email address has one hard bounce, emails will no longer be sent to that address. Subscribers with a hard bounce will be indicated on the Active Subscribers page with a red exclamation mark icon in the Status column. LibraryAware will not attempt to deliver emails to subscribers that have a hard bounce or a red exclamation mark in the Status column.

Below are some example situations along with the result and the impact on future delivery of emails.

Example SituationResultImpact on Delivery
Invalid email addressHard bounceNo more emails sent to that address
Mailbox over its size limitSoft bounceThat publication will not be sent again but future publications will be sent
Mailbox over its size limit and multiple email promotions are sent to that subscriber before he or she fixes the Inbox size problemAfter five soft bounces the subscriber will be marked as having had a hard bounceNo more emails sent to that
For each promotion you can view the number of emails that have bounced and which email addresses bounced at the Promotional Reports page.

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