I have an email server dovecot/postfix and he is not recording traffic data from email accounts. According to the changelog for version 3.0.5, this should be supported.
"Mail is reporting traffic dovecot servers."
The installation of my server was based in this howto: http://www.howtoforge.com/perfect-se...ot-ispconfig-3
About my server: Dovecot, Postfix, Centos 6.4, ISPConfig 18.104.22.168