The study investigates 60 young people aged 18 to 30 who are familiar with mobile phone e-mail (Keitai-mail) practices in Japan (a 1-to-1 ratio of male and female, the participants’ domiciles in several big Japanese cities) using a questionnaire on how they feel about CMC communication, in order to elucidate one type of widely used communication methods in the time the IT has been offering the variety of communication platforms. The result shows that senders are ruled by the norms entailed in Keitai-mail communication: Keitai-mail should be responded to immediately but should also be a complete sentence or message. In addition, the expressions used in Keitai-mail vary based on the interlocutors, making Keitai-mail a heavily context-dependent communication medium.