It is the second option, it should be root@
To change this I think it may be in either of two places. First is in pine. There is a configu option off teh main menu. I think you have to typ s for setup (not sure). Then in there is a reply to address. See if that is set correctly.
If that isn't it, then it is possible that you domain info is incorrect in either /etc/hosts or /etc/hostname. I am not terribly familar with turbolinux, I use mostly solaris.
If I had to guess, I think the pine seeting is where it needs adjusting.
If you want to verify that sendmail is running, you can telnet to the service. This is simple.
Type:
telnet localhost 25
This will telnet to port 25 (SMTP) on your localhost. Then you should be able to type helo, it it should respond with telling you what its server name is.
To get out, you can either type quit, exit. If neither of those work, then you can type ^] (which is control-key and right bracket "]"

. Then type quit and you should be returned to your command prompt.
Hope this helps you out!