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Email Bounces

Contact Lists Delivery Updated on July 6, 2021

Email addresses to which email campaigns fail to be delivered are marked as bounces. These email bounces are classified into three categories, soft bounces, hard bounces, and confirmed bounces. Common reasons for bounced emails could be a recipient’s server is temporarily unavailable, the email content was rejected, too many emails were being sent to the inbox, or the email address does not exist.

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Hard Bounces

Hard-bounced emails are email addresses that reject email delivery due to permanent failure; one reason could be the recipient’s email address is invalid. Hard-bounced emails will remain in your contact list as active contacts unless they change to a confirmed bounce. We strongly urge you to clean your contact list with our Clean List feature to remove email addresses that previously resulted in a hard bounce.

The following are some code examples given for hard bounces:

  • Mailbox not found
  • Mailbox no longer active
  • Unknown user
  • Incorrect domain
  • In some cases, an email is marked as a hard bounce due to spam filters.

  On occasion, valid emails could be classified as hard bounces, click here to learn more.


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Soft Bounces

Soft bounces are email addresses that reject email delivery due to short-term issues with the recipient’s inbox. Soft-bounced emails will remain as active contacts in your list. Emails sent to these addresses may experience temporary delivery delays or may permanently bounce. If you are experiencing a high bounce rate, removing soft bounces from your contact list with our Clean List feature can help prevent future hard bounces. Another option is to make a new list of the soft bounces and use a list verification tool to verify they are indeed valid email addresses.

The following are some code examples given for soft bounces:
  • Quota exceeded
  • Too many sessions in a connection
  • Temporary local problem
  • Out of office autoreply

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Confirmed Bounces

Confirmed bounced emails are email addresses that hard bounced on three consecutive email campaigns. All confirmed bounced emails are excluded from your active contact count and will not be emailed if the contact list they are in is selected for an email campaign. If a previously bounced email is opened in another campaign before it has been flagged as confirmed bounce, that contact’s bounce counter resets to zero. This allows bounced emails to remain in the active contact count instead of flagged as a confirmed bounce.

Confirmed Bounce contacts are listed separately in your contact list.

The following are some code examples given for confirmed bounces: 

  • 550 No such user (xxx@xxxxxxxxxxxx) Giving up
  • 5.1.1 unknown or illegal alias: xxxx@xxxxx
  • Recipient address rejected: User unknown

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Invalid Emails

Some emails that are considered invalid will not appear as a type of bounce. Instead, they are flagged as invalid emails and added to your Master Invalid List. Invalid emails are undeliverable. To learn more about how we categorize invalid emails, click here. 

To prevent hard bounces, you can utilize a list verification service to detect and remove invalid emails from your list. Benchmark also provides an easy-to-use Clean List feature that removes soft, hard, and confirmed bounces based on the recipient’s history.

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If you have any other questions regarding bounces, please feel free to contact our Support team via email, LiveChat, or by phone.

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