Systems and methods for obtaining availability status in respect of a plurality of user identifiers are provided. For each user identifier, a respective SIP cluster identifier is obtained. The user identifiers are then grouped according to SIP cluster identifier, each such group of user identifiers containing at least one user identifier for which the same SIP cluster identifier was obtained. For each SIP cluster identifier for which there is a group of user identifiers, a request is sent for availability status information in a single message to a SIP cluster associated with the SIP cluster identifier, the request containing the user identifiers of the group of user identifiers. A response to each single message is received in a single message containing availability status information for the user identifiers belonging to the group of user identifiers.