I am getting a RFC error message like this below
:u201D RFC_ERROR_SYSTEM_FAILURE: An exception occurred that was not caught.: com.sap.aii.af.rfc.afcommunication.RfcAFWException: error while processing message to remote system:com.sap.aii.af.rfc.core.client.RfcClientException: JCO.Exception while calling Z_XI_SEND_MAIL in remote system (RfcClient[RFC_REJECTION_MAIL]):com.sap.mw.jco.JCO$Exception: (104) RFC_ERROR_SYSTEM_FAILURE: An exception occurred that was not caught.u201D
Here Z_XI_SEND_MAIL is a customised function module which is calling some classes. This function module is responsible for sending emails to a group of people. This function module is working fine in acceptance server and development server but throwing exception in production. Thus the users are unable to receive emails. There has been no code changes in the function module. Idocs are being triggrred from sap r/3 system into XI, then being processed by a BPM, finally RFC (Z_XI_SEND_MAIL ) is being called to send email messages. SXMB_MONI is showing that the email message is being send to the RFC properly but communication channel is showing the above mentioned error.
Please suggest me what might be the reason of such errors?