A data transmission device, method and program capable of increasing work efficiency in data transmission during multi-destination delivery by unifying transmission method. According to the data transmission device, method and program, a user's instruction is received to designate for each destination one of a first transmission mode in which a file is sent attached to an e-mail message, a second transmission mode in which a file is sent to a file transfer server, and a third transmission mode in which a file is sent to a file transfer server and an e-mail message having a text string including address information of the file transfer server is sent, it is determined whether or not the destinations include those for which the first transmission mode is designated as well as those for which the second transmission mode is designated, and then the third transmission mode is set for the destinations for which the first transmission mode is designated in place of the first transmission mode when it is determined that the destinations include those for which the first transmission mode is designated as well as those for which the second transmission mode is designated.