Re: Knowing what you are doing
An easier route would be to use Webmin
You need to be very careful using Webmin if you're running sendmail.
sendmail has a mahine-readable config file called sendmail.cf. It's generally a bad idea to try to configure it with that; it's a very terse format. Instead, most of us humans use the easily-readable sendmail.mc file, and then build the sendmail.cf from that (using the m4 macro processor).
But Webmin edits sendmail.cf directly; this means that, if later you do something to sendmail.mc, you end up throwing away all your changes. That can be a little embarassing...