23.7.2.4 Server-Host Specification

You can further identify the specific service being requested in a filter by including server host name or address information in the serviceSpec entry. In that case the entry has the form:

service@hostSpec

You might want to use this feature when your Messaging Server host machine is set up for multiple internet addresses with different internet host names. If you are a service provider, you can use this facility to host multiple domains, with different access-control rules, on a single server instance.