Copy all mails marked as ***SPAM*** to specified maildir

==== Required information ====
- iRedMail version: 0.8.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP-PRO 2.1.2
- Linux/BSD distribution name and version: CentOS 6.5
- Related log if you're reporting an issue: N/A
====

How can I make "on the fly" coping of all incoming (from local users and inet) marked by amavis/spamassasin as SPAM messages  to a specified maildir? Not only "my" messages (this done through dovecot sieve) but all server`s incoming.

I want spam emails quarantine too, so spam_quarantine_to is not applicable.

Thanks for help.