Hard bounce
From ASSPSMTP
A hard bounce is a type of Non-Delivery Report that indicates a mailbox delivery issue (the address or domain doesn't exist, etc.), a delivery failure due to administrative policy (intentional blocking, spam filtering, etc.), or a routing failure that did not succeed after extensive mail queuing. Hard bounces typically require administrative intervention on the recipient side.
Hard bounces are 5xx/5.x.x series status codes.
Typical hard bounce verbiage:
- Blocked
- Domain not found
- Failed
- Failure
- Nondeliverable
- Relay
- Returned
- UBE (unsolicited bulk email)
- UCE (unsolicited commercial email)
- Undeliverable
- Unknown user
- User unknown
- spam
These icons link to social bookmarking sites where readers can share and discover new web pages.
