With recent versions of SmarterMail use Core 8, it has it's own webserver listening locally on port 17017.
IIS is now only used as the internet faced web service acting a reverse proxy to SM web server.
So yes, as long as the SmarterMail service is running, you will be able to join its webserver locally on port 17017.
Well at least that's how I understand it.
Sébastien Riccio
System & Network Admin
https://swisscenter.com