For those who don't want to read another thread - disable Anti Virus in the GUI and then reboot the system.
Restarting Zimbra wasn't enough in my experience, you need to restart the entire server.
To all who still having a problem with the clamav on zcs 5.0.16 just review my post
and it's important to run this command
it must be linked toCode:
ls -l /opt/zimbra/clamav
lrwxrwxrwx 1 root root 16 Apr 9 12:39 clamav -> /opt/zimbra/clamav-0.95.1
thank you so much raj, save me from several complains.