ADDRESS_LIST_UNAVAILABLE

What it means

Every full list of the delivery points at a postcode is derived from a postal operator's own address file, and serving it needs a licence. Where an open national register publishes its streets, the endpoint answers those streets at the postcode instead, with no house numbers; a country with neither answers this code. Spaw says so plainly rather than answering an empty list, which would read as "there are no addresses at this postcode".

For the same reason a covered country answers it for a postcode its listing cannot speak for, and the message says which case it is: a code outside the register's area (Northern Irish BT, forces BFPO and BF, and non-geographic BX codes are outside Ordnance Survey's Great Britain data), a postcode in a part of the country no installed register covers (Germany outside Berlin, whose other registers are filed by town, or a Belgian region whose register is not installed), a postcode the installed register cannot vouch for (a British district Open Names files no street under, since Ordnance Survey files each road under one district), and a postcode where a register whose coverage is complete holds addresses but none on a named street, as in many Czech villages. An empty list is answered only where the registers' coverage is complete and none of them holds an address at the postcode, and it is free too.

The rest of the address API does not depend on it. Validating an address, its postcode, its type and its risk signals all work from the datasets Spaw ships and syncs, and are unaffected by this code.