how to open a dynamic mail group?

==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.2
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):MySQL
- Web server (Apache or Nginx):Apache
- Linux/BSD distribution name and version: Ubuntu 14.04.2
- Related log if you're reporting an issue:
====
I want to open some dynamic mail groups . can i do that ?

Also I want to hide some mail adresses into a mail group. how can i do that ?

Thanks