To eliminate the failure of electronic mail communication and to make mail communication to be efficient by detecting a radio reception level at the time of the transmission/reception processing of the electronic mail and executing the transmission/reception processing of the electronic mail when the level is judged to be a communication possible state.

A portable telephone set gives a transmission request to a transmission manager 4 from a mail system 1 with a compiled transmission mail as a transmission file with a mail transmission operation and inquires a radio level detection module 7 of a radio reception level. The module 7 receives it and gives the transmission request of a transmission file to a transmission module 5 from the transmission manager 4 when a communication possible state is stable for not less than prescribed time in a timer module 6. The transmission module 5 extracts and transmits transmission data from a transmission file. When the response of the module 7 is impossible, the transmission manager 4 pools the transmission file in a spool 8 and takes it out and transmits it when it becomes the communication possible state.