==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.8.6
- Linux/BSD distribution name and version: CentOS release 6.8 (Final)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? No
- Related log if you're reporting an issue:
====

Hello folks, I've been runing iredmail for over two years now I think. Awesome combo of functionality, props to the developers.

My problem right now is a lot of emails with viruses are going through to my users.
Most of the users read their mail from gmail, and gmail is tagging our mails as spam, because of the virus and spam mails the the users get.

2 Weeks ago i set this configuration in amavis:

# Set default action.
# Available actions: D_PASS, D_BOUNCE, D_REJECT, D_DISCARD.
$final_virus_destiny      = D_DISCARD;
$final_banned_destiny     = D_DISCARD;
$final_spam_destiny       = D_DISCARD;
$final_bad_header_destiny = D_DISCARD;

Worked pretty well, but I still have virus and spam (a lot less now) going through. I cannot talk to gmail without first fixing this. And I'm out of ideas.
How can I improve my filters to be good enough?

Thank You,
Jorge.