Which term describes when an email is not successfully delivered or is rejected by an inbox provider?

In the world of email marketing, the term "Bounce" is used to describe a message that was sent but could not be delivered to the recipient's inbox. This happens because the recipient’s mail server (like Gmail or Outlook) rejected the email for a specific reason. Bounces are generally categorized into two types, and understanding the difference is key to keeping your sender reputation healthy: Hard Bounce: This is a permanent delivery failure. It usually happens because the email address is invalid, fake, or the domain doesn't exist. Klaviyo automatically suppresses these profiles immediately so you don't try to email them again, which protects your reputation.