To enable a sender to determine which file is printable among a plurality of printable and unprintable files attached to one electronic mail.

A decision part 104 determines whether each of the plurality of received files is printable or not. An electronic mail transfer part 103 selects an unprintable file from among the plurality of files on the basis of decision results of the decision part 104, and generates transfer mail including information to specify the unprintable file, and then transfers the mail to a predetermined destination.