When a destination pincode is not part of a courier's standard beat, it is flagged as ODA. The parcel may be delivered via a partner network or from a distant hub, adding an ODA surcharge and extra days. Some pincodes are outright non-serviceable, meaning the order cannot ship on that courier at all.
Checking pincode serviceability at checkout — and routing ODA pincodes to whichever courier actually covers them — prevents both surprise surcharges and orders that can never be fulfilled.