Have a look at the following
http://linuxdocs.org/HOWTOs/Mail-Adm...tor-HOWTO.html
http://linuxdocs.org/HOWTOs/mini/Mail-Queue.html
They might help a little. As for the error message about the file. Post the message someone might be able to help more.
When you say you are trying to setup a mail server you want to setup a machine that relays mail (Sends) and a machine that users can connect to with say Outlook to check their mail yeah? This ins't too difficult... Have a look for documentation on Sendmail for the relaying. It can get a bit scary though - not the nicest config file.
Its probably worth searching the forum too, I know that I've answered a few questions in the last couple of weeks that have been along the lines of setting up a mail server.
HTH
Jamie...