What is the difference between a hard bounce and a soft bounce?

Mail status like soft bounce and hard bounce appear from time to time. But what do they mean?

When Netcore Email API attempts to deliver your emails, the delivery of the email could fail due to a few recipient related reasons.

Hard Bounce: If the delivery of the email fails due to permanent failure, the email is said to be hard bounced. Some of these failure reasons can be:

  • The email address doesn't exist.
  • The recipient domain doesn't exist. For instance - your emails to [email protected] are going to fail if the domain 'sample.com' doesn't exist.

Soft Bounce: If the delivery of the email fails due to temporary failure, the email is said to be soft bounced. Some of these failure reasons can be:

  • The mailbox was full (the user is over their quota).
  • The recipient's server was down.
  • The email was too large for the recipient's inbox.
  • The recipient server is currently not accepting emails from the sending IP address.

We do retry delivery of emails which have failed due to soft bounce. But, it is always recommended to keep your bounce rate below 5%, as more the bounce rate, the more negative your reputation with the ISPs.

Related Resources

Was your mail actually delivered? How to find out?


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