X_WEBHOOK_DELIVERY_REJECTED
Means
the endpoint refused the delivery in a way a retry cannot change
Typical cause
a 4xx that is not a throttle, or a redirect. Its own code rather than a per-instance flag on the row above: classifyThrown reads a per-instance terminal on an unregistered code as UNCLASSIFIED, so the distinction has to be a registered code or it does not exist
Fix
x jobs show <id> --json — meta.status is the answer; then correct the url or the secret on this endpoint row in your own table. A 401 or 403 is a secret the two sides disagree about, a 404 is a path that moved