An image data communication apparatus is connected to an image data source and to a network, and transmits image data attached to an e-mail to a receiving apparatus via the network. The e-mail including a mail from command and a mail message. The image data is attached to the e-mail as an openable document. The image data communication apparatus comprises a memory which stores default information and information regarding an identification of at least one user, and a panel section which selects information regarding an identification of at least one user other than the default information stored in the memory. The image data communication apparatus comprises a controller which sets the default information into the mail message of the e-mail to which the image data is attached when the information regarding the identification of the user is not selected by the panel section, and sets the information regarding identification of the user selected by the panel section into the mail message of the e-mail to which the image data is attached when the information regarding the identification of the user is selected by the panel section.