1. A method for accessing, from a third-party communicating entity, a communication managed by a host communicating entity and established between the host communicating entity and at least one participant communicating entity via a packet network, wherein said method comprises: transmitting a message from the third-party communicating entity to the host communicating entity, the message comprising at least one mixing parameter having one of a plurality of different predefined values, each different predefined value prescribing one of a plurality of different restrictive mixing policies, said mixing parameter being associated with an identifier of a participant communicating entity, wherein said third-party communicating entity does not yet have access to the communication established between the host communicating entity and the at least one participant communicating entity when said message is transmitted; and applying, while maintaining the communication established between the host communicating entity and the participant communicating entity, one of the plurality of different restrictive mixing policies on communication flows exchanged between the participant communicating entity whose identifier is associated with the mixing parameter and the third-party communicating identity, said applied restrictive mixing policy being determined by the value of the mixing parameter and the identifier associated with the mixing parameter.