MESSAGING SYSTEM FOR INDICATING STATUS OF A SENDER OF ELECTRONIC MAIL AND METHOD AND COMPUTER PROGRAM PRODUCT THEREFOR

An electronic mail computer program running as a client application permits a user to determine in a single user interface application window, for example an “in-box,” the on-line status of those persons who have sent e-mail messages to the user. Once such a sender has been identified as being currently on-line and available for real-time messaging, the user may use the same application window to initiate real-time messaging with the sender. The client application cooperates with a messaging system server that manages and provides the on-line state of senders of electronic mail to the user's client computer, including for example the following states: on-line, off-line, do-not-disturb, and accepting real-time messaging.