Hiding headers

I notice that when I go to a privacy site and look at the headers I display, my server domain name is listed in the http_via header. This is a bit of a privacy issue on every site I visit. I can hide all headers using the anonymous option, but this creates problems when trying to access certain forms on web pages. http_via does not seem to be a valid header when I try to stop it displaying using webmin. Can anybody tell me the name of the header which displays the domain name, or an option for SME which will cull certain headers and do the equivalent?

Thanks
Russell