Enterprise mobility and IP multimedia system corporate services are becoming more relevant; in particular, the IMS-based presence service is starting to provide different kinds of seamlessly mobile services, with context awareness in a wide range of enterprise-deployment scenarios. However, the deployment of presence-based enterprise services in wide and heterogeneous wireless networks still faces several challenges. First of all, scalability and differentiated quality are considered crucial, especially under heavy traffic conditions and when dealing with inter-domain mobility scenarios. This article presents an overview of very recent research contributions about the standard IMS presence service and some novel proposals for scalability and quality optimization. In addition, we propose a novel presence service solution that presents three original extensions for scalability and quality: a federated model to optimize inter-domain distribution of notification messages through locality-based aggregation, a proposal for differentiated quality levels, and an extension of client-side buffering for reliable delivery of presence messages, even during user roaming. The prototype of the enhanced presence service has been deployed and validated by obtaining performance results of improved scalability in terms of CPU and memory usage in infrastructure nodes and message traffic. The prototype is openly available to the IMS community for possible refinement and extension.