==== 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 installer
- Linux/BSD distribution name and version: Debian 9
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I've had a stable iRedMail system running for a few days now, some of the previous posts in this forum have been invaluable.
I'm now fine tuning so have a couple of questions.

I want to check if mail is being scanned for spam, what the thresholds are and what the system does with it. There's no dovecot.sieve.sample file as shows in the FAQ's, however dovecot.sieve shows:

if header :is "X-Spam-Flag" "YES"

Looking at the source of incoming mail, this header is not present. Is it only added if the mail is detected as spam? i.e. should there be a "X-Spam-Flag" "NO" for everything else?

I see this is added:
X-Virus-Scanned: Debian amavisd-new at REMOVED

Lastly, it is the default behaviour for amavisd (on Debian 9) to use the DKIM key for your primary domain for all additional domains set up in iRedMail. Does this cause any issues? I've not yet added txt records to the DNS of any domain hosted on the iRedMail server, so have not tested if this causes any problems. I'm still getting to grips with how DKIM works.

Thanks.