Please note this information is probably out of date.
Alternative Postfix RPMS are available from various sources:
Red Hat
http://www.redhat.com:
RedHat now provide Postfix rpms as standard with both Fedora and
RedHat Enterprise Linux. Originally this was not the case and was
one of the reasons I started packaging postfix for RedHat as there were
few alternatives. However, unless you need a special configuration
not supported by RedHat out of the box you are probably
best using the Postfix rpm which comes with your RedHat distribution.
If you notice that any of these links become out of date, or wish to provide
me with links to other Postfix packages I haven't included here then please
let me know.