http://www.digitalfaq.com/forum/guides-ispconfig/3261-how-optimize-ispconfig.html
vi /etc/postfix/main.cf
# content_filter = amavis:[127.0.0.1]:10024
# receive_override_options = no_address_mappings
/etc/init.d/clamav-daemon stop
/etc/init.d/clamav-freshclam stop
/etc/init.d/spamassassin stop
/etc/init.d/amavis stop
update-rc.d -f clamav-freshclam remove
update-rc.d -f spamassassin remove
update-rc.d -f amavis remove