These two questions are quite academic until the machine from which
you are sending the mail knows how to find the machine to which you are
trying to send the mail.
The machine from which you are sending the mail is trying to send it to
a machine called "mailhost", and it is getting told by its nameserver
that it doesn't know about any machine called "mailhost".
Until you solve that problem, you might as well be running a copy of
MS-DOS 1.0 on the other machine.
Forget about sending mail until, on the machine from which you were
trying to send it, you can do:
ping mailhost
and get replies.
Perhaps the problem is that the machine to which you are trying to send
mail isn't called "mailhost" at all (in which case you will never get
there by sending to "mailhost"). If it's called, for example, "george",
then from the other machine you need to be able to do:
ping george
and get replies. Once you get that far, try sending mail, and there's
a good chance that it will work.
Depending on what version of Linux you are running, your MTA (Mail
Transfer Agent) is probably sendmail. Other possibilities are exim and
qmail. But this is completely irrelevant until the two machines are able
to ping each other.
-- ted@psg.com http://psg.com/~ted/ (Ted Powell) "If you don't have the source code, you are probably going to be screwed in the long run." --Philip Greenspun