A data transmission system in which a registration server on which recipient information is registered is connected over a network to a data transmission apparatus that transmits data to a recipient, comprising: the registration server, comprising, a database in which information including recipient information is registered, a search portion that searches the registered information using search parameter, and a communication portion that outputs the recipient information resulting from the search by the search portion to the data transmission apparatus; the data transmission apparatus, comprising; a storage portion that deems recipient information sent from the registration server to represent a recipient and stores the recipient information in association with a recipient designation key, a display portion that displays a recipient setting screen that displays the recipient designation keys stored in the storage portion, and a transmission portion that transmits data to the recipient corresponding to a selected recipient designation key; wherein the registration server or the data transmission apparatus has a search parameter value storage portion that stores the search parameter.