Error handling in ABAP proxies

Hi,

Please let me know the different ways by which error handling can be done (both at XI side and also the SAP R/3 side) in the case of ABAP inbound and outbound proxies.

Basically

1. In the case of message posting to SAP R/3 using ABAP proxy (Inbound to SAP), how errors generated in SAP can be monitored/notified and sent back to source system or XI system

2. In the case of proxy message being received by XI, from SAP, if errors are generated in SAP (before posting), how the errors can be monitored and notified.

Your early response is appreciated.

Regards

Venkat