*.rar files should be sent with the Content-type of application/x-rar-compressed. They are currently sent as text/plain. I suggest adding the line: application/x-rar-compressed rar to conf/mime.types.
Our policy for mime.types is listed here: http://httpd.apache.org/docs-2.0/mod/mod_mime.html Essentially, it says that we'll only add IANA registered types. This type is not registered. Please let us know if it does become a registered type and we will consider adding it. Thanks.