There are different options for communication between the SAP System and the program Mlunxsnd which handles the forwarding of messages to be sent to the mailing program. These depend on which activation type the RFC link was created with:
Program Mlunxsnd is automatically started from the SAP System by SAPconnect when required. The SAP Internet Mail Gateway runs either on a SAP application server or on an separate computer. In the last case, the program is either called via remote shell, or an SAP stand alone gateway is installed.
The program Mlunxsnd is registered as an RFC server on the SAP application server. It is also started manually and then runs as a daemon process on the application server.
For further information on theRFC interface, see the BC documentation - The RFC API.