Files with the .RPMSG extension contain e-mail messages with assigned specific access permissions. The data stored in the file includes both the content of the message and the attachments, as well as information about the users chosen by the sender to be able to read, print, copy or forward the message.

E-mails with specific access permissions are sent as RPMSG attachments to regular e-mails, and their encryption limits the access to solely chosen users that have logged in using their name and password.