The receiving system can best tell you what that means.
However in my past I have seen:
CA mean Commit Accepted when the integration piece is committing to the application DB. Ususally there will be 2 acknowledgments in this case. One that indicates the message is received (AA) and then the CA.
CA mean Conditionaly Accepterd. I had this when the receiving system wanted to indicate the message was accepted but there was an issue which would be logged in their application log.
email: jim.kosloskey@jim-kosloskey.com 30+ years Cloverleaf, 60 years IT – old fart.