RFC Destinations need to be created to allow TE to communicate from the domain controller system to all participating SAP systems.
They must be named TRANSPORT EXPRESS XXX where XXX is the system ID of the SAP system being connected to and be allocated with a TE RFC user.
For non-ABAP (Portal, Java) systems the RFC destination must point to the CTS+ domain controller.
In addition, for things like in-line conflict analysis a further RFC destination is required to connect back from the participating system to the TE domain controller. These need to be setup in the relevant (development) systems and be named TRANSPORT EXPRESS CONTROLLER. A domain controller RFC user will also be required for this purpose.
Please refer to the TE Administration Guide for more information about RFC destinations.