Manikandan,
FYI, PI PGP is uses default signingAlgo:SHA1, default encryptionAlgo:CAST5.
In receiver channel, you have not used https URL and PGP module. So PI is sending simple http request. If Salesfoce cloud server is rejecting it, then you are positing it to wrong URL or you should be sending https. You can use SOAPUI to test SF service.
Please post the error message in PI and request error log from SF admin team.