The present invention provides an email multicasting device which changes a distribution interval of emails dynamically in accordance with the number of emails to be multicast. The email multicasting device pre-stores on a client basis, mobile numbers of users which are destinations of an email. The email multicasting device, when receiving mail contents from a client, creates plural emails each of which contains the mail contents and one of mobile numbers associated with the client, and queues the emails in a buffer area. The queued emails are distributed sequentially at predetermined time intervals by the email multicasting device.