Description of problem:

In the event of any errors on the clamav update cron job (or warnings or any
output at all) all of the following system users are mailed:

root,postmaster,webmaster,clamav

Standard in fedora would be to just email the root user. 

The clamav user is very unlikely to ever read emails. 
webmaster shouldn't be concerned with a non web server process. 
postmaster is aliased to root in the default install.