postfix (or one of its subpacakges) has multiarch conflicts when installed for both i386 and x86_64 in the Fedora development tree. For help in resolving them, see http://fedoraproject.org/wiki/PackagingDrafts/MultilibTricks.
file /etc/postfix/makedefs.out from install of postfix-2.4.5-2.fc8 conflicts with file from package postfix-2.4.5-2.fc8
(Note that this is an automated bug filing.)
It would be nice to have these bugs fixed by the beta of Fedora 9.
Fixed in rawhide in package postfix-2.4.5-3.fc9.