I know, this is [normally] an RTFM question, except, well, we're talking about Authorize.net so the FM is hardly R-able.
I noticed when looking at the all the fields that get sent during the Silent Post, Authorize.net returns an item called "x_cust_id". It is not addressed in their sample code, and I can't find out where in the XML document that field would get posted. I'd like to use it!
So, how exactly do I add "customer Id" when I create a new ARB subscription?
Furthermore, is there any documentation that actually shows all the information I can send to ARB? I don't even know what my options are!