~pp~
See helpful install directions at:
http://tomclegg.net/qmail-linux

Uninstall sendmail if necessary. Telnet to port 25 to ensure it's not being used.
To stop sendmail:
/etc/rc.d/init.d/sendmail stop
To uninstall it:
rpm -q -a | grep "sendmail"
Now uninstall (SENDMAIL_PACKAGE_NAME is of course the name returned by the previous rpm -q command.
rpm -e SENDMAIL_PACKAGE_NAME

~/pp~