Postfix

Postfix postfix-2.5.5 is updating from an incompatible version: Ebuild shows the following error

 * If you want minimal downtime, emerge postfix with:
 *     FORCE_UPGRADE=1 emerge --buildpkgonly postfix
 *     /etc/init.d/postfix stop
 *     emerge --usepkgonly postfix
 * Then run etc-update or dispatch-conf and merge the configuration files.
 * Then restart Postfix with: /etc/init.d/postfix start