address_needs_review | Correct missing unit or recipient details. |
document_overflow | Shorten text or split the document. |
invalid_dimensions | Export a correctly sized print-ready PDF. |
quote_expired | Refresh the quote and inspect the new total. |
idempotency_conflict | Reuse the original payload or choose a key for a genuinely new operation. |
insufficient_funds | Ask the customer to fund the account. |
provider_pending | Poll the existing mailing. Do not create another. |
live_unavailable | Use sandbox; live sending is not configured. |
cancellation_too_late | The mailing cannot be recalled. |
rate_limited | Wait for Retry-After before retrying. |