What steps to start PostFix on Linux Red hat 9.0

Hi,

I's like to build a mail server with PostFix based on Linux Red Hat 9.0. I've posted a question to get your comments on which mail server I should use (Q_20961132).

I read through the documents and manuals for installation and configuration on the web site: postfix.org.
They have very good documents. I also looked into some books on PostFix to get some more ideas about PostFix.

Then I started. I looked into the Linux Red Hat 9.0 box and found out: it seems that the PostFix has been installed on the Linux Box. I checked with "rpm -qa : grep postfix" and got "postfix-1.1.12-1"

I also checked if the popular mail server "sendmail" is running or not with "ps -ef | grep sendmail" and I got:
"... sendmail: accepting connections" and "... sendmail: Queue runner ..."

When I read through the documents and manuals of PostFix on www.postfix.org and also in the books, maybe we need to replace 3 files: (1) sendmail (2) mailq  (3) newaliases

After reading some of these details, my mind jumps ahead a bit and start questioning: after replacing these files with those of PostFix, how to check if PostFix is really running on the box or not?

May you give help on this?

Thanks,

Rfr1tz