Disclosed is a communication apparatus in which it is possible to change the size of data transmitted at one time, the data size being changed to one size in case of transmission of e-mail via a mail server and to different size in case of transmission that is not performed via a mail server. E-mail data having image data as an attached file is generated and it is determined whether a predetermined server will intervene when e-mail is transmitted to a transmission destination. When it has been decided that the destination will be a mail server, it is determined whether the e-mail data has exceeded a prescribed size. E-mail data for which it has been determined that the prescribed size is exceeded is divided into a plurality of segments and then the e-mail data is transmitted to destination decided.