This disclosure relates to specifying a sender in detail when image data is attached to email and transmitted from an Internet facsimile device. An MFP (100) has an E-mail transmission mode in which email with an image is transmitted to a general email address, and an IFAX transmission mode in which email with an image is transmitted to an apparatus copying with the IFAX function. In transmitting an image, the MFP (100) authenticates the user in cooperation with an authentication server (102). When the authenticated user selects the IFAX transmission mode, an email address corresponding to the user is acquired from the authentication server (102), and set in the Sender field. The From field holds the email address of a device, similar to the prior art.