1) Amavisd does not install when postfix rebuilt with antispam/antivirus checked.
Installation of amavisd-new (yum install amavisd-new) fails because it requires package lzop which is unavailable in the distribution.
There is no warning message that amavisd did not install. No mail is delivered to email accounts.
2) lfd continually throws error emails to root in /var/spool/mail/root. Unless mail is installed (yum install mail), a new user might not notice these mails, but eventually they will eat up disk space. On my test system, 40 emails per hour are posted to root.
As far as I can tell, Centos 6.6 is unusable if the email stack in built to include amavisd.