I need help with setting up a sieve filter that runs for every user, how to do that ?

Why does the container delete spam by default ? I missed some important mails because of that (false positive). The log shows they hit a score of 8 and got rejected.

I now configured Spam handling the following way:

• Setting env SA_KILL to 1000 which prevents blocking / deletion of spam mails.
• Running docker exec -it mail sed -i 's/mailbox Junk {/mailbox Spam {\n auto = subscribe/g' /etc/dovecot/conf.d/15-mailboxes.conf
  which will create the Spam folder for every User automatically and marks it as Junk
• setting up a sieve filter for every users to move Spam into the Spam folder
  cat << 'EOF' > /srv/mail/config/[email protected]
  require "fileinto";
  if header :contains "X-Spam-Flag" "YES" {
  fileinto "Spam";
  }
  EOF

However i would prefer to just create 1 Sieve filter which gets applied to all Users. That should be possible but i don't know how. Could somebody please help me with it, thanks.