Setting iReceivable access for external customer/user

Dear iReceivable Guru,

We are implementing iReceivable application and have question on our Customer access to our iReceivable application.

We are on release 12.1.3

We are using SSO for our EBS release 12.1.3

We have our DMZ implemented already for our iSupplier application.

We are live with our iSupplier application and this application does not use SSO for our external users.

We would like to use the same setup for iReceivable application.

It seem we moght missing a profile option or something.

We are able to register our iReceiable users. However, after they receive and hit the url they go to our SSO url rather than our local url.