Hi Mark,
In my other reply I left a wrong URL, the correct is:
http://help.sap.com/saphelp_nw73/helpdata/en/3b/dec6eaf3ac42fba8f92f2413ec930f/content.htm
The RFC destination LCRSAPRFC is required for the connection to the System Landscape Directory (SLD). It is used to read the exchange profile.
The RFC destination SAPSLDAPI is required for the connection to the SLD. It is used by the ABAP API.
Only RFC SAP_PROXY_ESR is used to connect to ESR (PI).
http://help.sap.com/saphelp_nw04s/helpdata/en/be/6e0f41218ff023e10000000a155106/content.htm
Regards.
Rodrigo.