c# - how to set up production credentials on behalf of third party -

we need in understanding how set production side of integration. suspect may not able set in way had anticipated (although there workaround). way of background:

we have written custom application our customer intended allow customer send envelopes directly custom application have written them.

where may have problem, anticipated envelopes sent using customer's existing docusign account.

we using soap api c# application. our testing credentials set in c# per following pseudo code:

... credentials.accountid = " our account id here "; credentials.username = "[ our integrator key here ]" + "our email address"; credentials.password = " our password "; credentials.apiurl = " demo api url "; ...  // elsewhere when define envelope  envelope.accountid = " our account id here "; 

now, in production do:

... credentials.accountid = " our customer's account id here "; credentials.username = "[ our integrator key here ]" + [our customer's send on behalf of email address] + "our email address"; credentials.password = " our customer's password ";  // or our password perhaps? credentials.apiurl = " production api url "; ...  // elsewhere when define envelope  envelope.accountid = " our customer's account id here ";  

is attempting possible or must our customer move account on our account?

have federation http://msdn.microsoft.com/en-us/library/bb897402.aspx , reliant party trusts