1. my sender is HTTP POST . what should i configure in sender communication channel in SAP PI .like SOAP or HTTP .What are the parameters i need to pass .
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If you are on PI 7.3 and above, configure the HTTP AAE adapter - Configuring the Java HTTP Adapter on the Sender Channel - Advanced Adapter Engine - SAP Library
2.while using inbound proxy for encrypted data i need store the data in to table , the same proxy can i call another outbound service for decrypt same data.
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Yes you can always a proxy within a proxy.