We can call this service from any of the events available or just call this service from a Workflow.
Found this simple code on IT-toolbox :
var mailBS = TheApplication().GetService("Outbound Communications Manager");
var psInput = TheApplication().NewPropertySet();
var psOutput = TheApplication().NewPropertySet();
psInput.SetProperty("CommProfile", "Communication profile name");
psInput.SetProperty("MsgToList", "email ids to whom you want to send email");
psInput.SetProperty("MsgBody", "email content");
psInput.SetProperty("MsgSubject", "subject");
mailBS.InvokeMethod("SendMessage", psInput, psOutput);
Coming up Next: Steps to configure Communication Profile.