POstfix deferred folder count high

Try using mailq command to see what the issue is

try this first:
service clamav-daemon restart

If the deferred count is way up try this

Solution

Please restart both amavisd-new and Postfix and then check with
netstat -tap

that both are running on the ports
25 and 10025 (postfix)
and
10024 (amavisd-new).