Your email is permanently undeliverable to this email address because the address is either fake, was entered incorrectly, or the user mailbox or domain is no longer active.
For example, the following are hard bounce error messages:
- Unknown or illegal alias
- Address rejected
- No such user here
- A bad destination mailbox address
- Rule imposed mailbox access for refused: user invalid
To know more about Email Bounces and Error Codes, click here