Many-to-many communication is a central component of widespread technologies like social networks and the IoT. For many applications, it is desirable that the anonymity of communication participants is preserved. We focus on the protection of sender anonymity in peer-to-peer networks that allow scalable group communication via publish-subscribe overlays. While DC-nets can be used for achieving sender and receiver anonymity for many-to-many communication, they also induce a considerable communication and computation overhead. We address this challenge by introducing a modified version of DC-nets that induces less overhead than classical DC-nets while preserving their sender anonymity properties. Moreover, we present challenges that arise when combining publish-subscribe overlays with DC-nets. We introduce a novel technique that addresses the presented challenges, hereby protecting the anonymity of senders during its initialization and runtime. As our approach allows for anonymization groups of configurable size, we also analyze how groups that are suitable for this purpose can be formed.