Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining availability statuses for users of a communication service provider system. One of the methods includes obtaining data identifying a plurality of availability status features for a user of a communication service provider system and a respective weight for each of the availability status features; determining a respective current value of each of the availability status features; and determining an aggregate user availability status based at least in part on the current values of the availability status features and on the weights for the availability status features.