vi /etc/postfix/main.cf
	header_checks = regexp:/etc/postfix/header_checks

sed -i 1i"/^Received:/ HOLD" /etc/postfix/header_checks

vi /etc/MailScanner/MailScanner.conf
	Run As User = postfix
	Run As Group = postfix
	Incoming Queue Dir = /var/spool/postfix/hold
	Outgoing Queue Dir = /var/spool/postfix/incoming
	MTA = postfix
	Sendmail = /usr/sbin/sendmail.postfix
	Sendmail2 = /usr/sbin/sendmail.postfix
	SpamAssassin User State Dir = /var/spool/MailScanner/spamassassin

mkdir /var/spool/MailScanner/spamassassin
chown postfix:postfix /var/spool/MailScanner/spamassassin
(and make sure /var/spool/MailScanner/{incoming,quarantine} are owned by postfix)

chmod 770 /var/spool/postfix/hold
chown postfix:postfix /var/spool/postfix/hold

mkdir /var/spool/mail_backup
chmod 775 /var/spool/mail_backup
chown postfix:postfix /var/spool/mail_backup