To provide an electronic mail transmission system for preventing an attached file from being forgotten to be attached.

This system is provided with a transmission document check means for confirming the contents of a transmission document, a character string registration means for storing a prescribed character string, an attached file check means for confirming the presence/absence of the attached file and a message generation means for generating a prescribed message. When transmitting the transmission document, the transmission document check means checks whether or not the character string is included in the transmission document. In the case that the character string is included, the attached file check means checks whether or not the attached file is included in the transmission document. In the case that the attached file is not included, the message generation means generates the message.