A data transmission apparatus capable of transmitting image data to a recipient using recipient's desired transmission parameters regardless of whether the recipient resides inside or outside an intranet to which the apparatus is connected, wherein the recipient is requested via an e-mail to designate the desired transmission parameters through the most appropriate transmission medium that is set in consideration of the recipient's location. Specifically, the transmission medium is set to a Web browser if the recipient resides inside the intranet to which the apparatus is connected, while it is set to an e-mail if the recipient resides outside the intranet.