==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.9
- Deployed with iRedMail Easy or the downloadable installer? downloadable
- Linux/BSD distribution name and version: Ubuntu 16.04 LTS
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? 3.1 MySQL
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I want to set this kind of managesieve rule but for an entire domain, not just for a single user.  Where would I add this?

require "fileinto";
if not header :contains "Received" "example.com"
{
    fileinto "Trash";
}