1. A method for providing a user directory for communication within a system, the method comprising: causing a client machine to display the user directory including a plurality of registered users with the system when a user logs into the system via the client machine, the registered users being represented respectively by identifiers and icons, wherein the user directory is received from a server machine in the system, wherein the server machine is provided to transport messages exchanged between or among some of the registered users and the user; allowing the user to browse the user directory being displayed on the client machine to view a status of each of the registered users, wherein the status is periodically updated; and causing the client machine further to display an image when a registered user in the user directory is selected by the user who desires to send internal mail to the registered user, wherein the image is an enlarged version of an icon associated with the registered user, the enlarged version of the icon is in a larger dimension than an original dimension of the icon and has no substantial changes to content in the icon, wherein the internal mail includes a recipient area and a message area, the recipient area is automatically filled to indicate a recipient being the registered user, delivery of the internal email is conducted without relying upon an email address commonly known to include an @ sign, and a user name or a domain name in the email address.