If you post a question concerning this function module, it is likely to be rejected on the grounds that you should be using the CL_BCS classes instead. These classes are well documented and there are many examples. They're also easier to use and don't have the problems that the function module is notorious for.
If you are having problems with emailing, then recast your program with the CL_BCS classes and try that. Only then post your problem.
If for some reason you are forced to use the function module, then you must state that in your post.