Sometimes i'm asking myself who the fuck is releasing some totally bugged packages… After several trials here what you need to do to get the EPEL clamav to run on CentOS 7:

yum install clamav-milter-systemd clamav-scanner-systemd clamav-update
cp /etc/clam.d/scan.conf /etc/clamd.d/clamd.conf

edit /etc/clamd.d/clamd.conf

LogSyslog yes
DatabaseDirectory /var/lib/clamav
TCPSocket 3310
TCPAddr 127.0.0.1
User clamscan
AllowSupplementaryGroups yes

Start it and enable for reboot

systemctl restart clamd@clamd.service
systemctl enable clamd@clamd.service

edit then /etc/mail/clamav-milter.conf

MilterSocket inet:7357
User clamilt
AllowSupplementaryGroups yes
ClamdSocket tcp:127.0.0.1:3310
LogSyslog yes
OnClean Accept
OnInfected Reject
OnFail Defer

start the milter now and on reboot

systemctl restart clamav-milter
systemctl enable clamav-milter