Yes, SM works fine with E-Smith, been using it for years. The release of the webmail component of E-Smith is probably just as good now, but I still prefer SM's overall appearance and functionality. The most recent release has additional features so make sure you grab that.
I did not use Charlie's RPM. I did try, but it didnt work out for me. No matter, the thing is simple to install and has a script providing a reasonable menu to configure your specifics. Just follow the README and you will be up in a matter of minutes.
I've found it handy (and just plain simpler) to install it in a suitably named i-bay. I can then control its user & internal/external access using the standard e-smith i-bay management.
Aaron