Postfix is a replacement for sendmail. Unless you install Postfix from source code the two cannot coexist on the same system. The error you're getting should look something like this:
[root@ntbox /root]# rpm -Uvh postfix-19990906_pl07-1.i586.rpm error: failed dependencies: sendmail conflicts with postfix-19990906_pl07 |
In order to get postfix to install you will have to remove sendmail first but there is a trick to doing this properly. Here's what to do:
(as root) mkdir /root/sendmail-old cp /etc/aliases /root/sendmail-old/ cp /etc/sendmail.cf /root/sendmail-old/ cp /etc/sendmail.cw /root/sendmail-old/ cp /etc/mail/* /root/sendmail-old/ rpm -e sendmail sendmail-doc sendmail-cf --nodeps killall sendmail rpm -Uvh postfix-19990906_pl07.i586.rpm |