Iuri: "Why does xml-rpc always answer with 302 at first?"
Probably, the xml-rpc package is mounted at your instance at __LOCATION__/RPC2/. As always in OpenACS, if one navigates to a mounted package via e.g. __LOCATION__/RPC (without trailing slash), one is redirected to __LOCATION__/RPC/ (with trailing slash).
In your case, when you change the URL in the RPC requester to http://www.evex.co/RPC2/ i would expect that the 302 redirect will disappear.
Hope this helps
-gn