WebMethods encoding options for Trading Networks

I received the below info as a request from a user. I have no clue, so please someone help!!!

In order to send files to Svetogorsk, I will need to use a couple of different file encoding schemes. One, which I already know is ISO-8859-5 which is required for any files going to the Svetogorsk MAJIQ Elixir System. What is the webMethods encoding option for 1251 (Microsoft Windows Cyrillic)? Is there a reference page somewhere online which describes which values are valid for this option?