1. A method for determining an applicable policy for an incoming message comprising a service-level addressing element, comprising the steps of: a) applying a potentially applicable policy to the incoming message to make the service-level addressing element of the incoming message accessible, b) if the service-level addressing element of the incoming message becomes accessible and is a service-level addressing element to which the currently applied policy is associated, determining the currently applied policy as applicable policy, and c) if not associated repeating steps a) and b) with a further potentially applicable policy, wherein the service-level addressing element becomes accessible when it shows a valid syntax, and, further comprising: applying the potentially applicable policy to the incoming message only to the extent that the service-level addressing element of the incoming message becomes accessible, applying the potentially applicable policy by applying an initial part of a transformation to the incoming message, which initial part of a transformation is prescribed by the policy, for an initial part of the transformation comprising transformation steps: processing an error evaluation after having processed a transformation step, applying the remaining part of the transformation to the message obtained by applying the initial part of the transformation on the incoming message, and rejecting the currently applied policy if the remaining part of the transformation fails; providing a definition for the initial part of a transformation before applying the potentially applicable policy comprising this transformation; before the potentially applicable policy is applied to the incoming message: determining policy components of the potentially applicable policy, determining whether a policy component is an address-transforming policy component or an address-retaining policy component, and including any address-transforming policy component in the initial part of the transformation; and including any address-retaining policy component in the remaining part of the transformation; joining equal initial parts of the transformations prescribed by the policies, applying the potentially applicable policy to the incoming message only to the extent that the service-level addressing element of the incoming message becomes accessible; applying the potentially applicable policy by applying an initial part of a transformation to the incoming message, which initial part of a transformation is prescribed by the policy; and for an initial part of the transformation comprising transformation steps, processing an error evaluation after having processed a transformation step.