When you add the MSMQT adapter, the host name it uses is the default host at the time – this will usually be BizTalkServerApplication – and once you’ve selected it, it seems you can never change it. So if you want a separate host for your MSMQT adapter, before you add the MSMQT adapter to your server group, create a host called MSMQT_host (or whatever naming convention you’re using for your hosts) and set it as the default host. Now add the MSMQT adapter, and it will run under this host. Then, reselect the previous default host, and set it back to the default host.