Apple Handy Guide

#restart apache server on Apple
sudo /usr/sbin/apachectl restart

#restart amavis
sudo /bin/launchctl unload /System/Library/LaunchDaemons/org.amavis.amavisd.plist
sudo /bin/launchctl load /System/Library/LaunchDaemons/org.amavis.amavisd.plist

# postfix
sudo postfix reload
or if you want master to reload
sudo /bin/launchctl unload /System/Library/LaunchDaemons/org.postfix.master.plist
sudo /bin/launchctl load /System/Library/LaunchDaemons/org.postfix.master.plist