A presence model is maintained for a messaging system to message among a
plurality of computing device users. A permission is maintained for
providing to a first computing device a presence indication for a user of
a second computing device. Based on an indication of a user of the first
computing device not being in a messaging list for the user of the second
computing device, the permission is maintained to provide only a basic
presence indication to the first computing device for the user of the
second computing device. From the first computing device, a message is
caused to be sent to the second computing device. Based on the maintained
permission, the basic presence indication for the user of the second
computing device is provided to the first computing device and a user
interface element is provided via which the user of the first computing
device can be added to a messaging list for the user of the second
computing device.