If you chose to store mail accounts in OpenLDAP, then you can try the iRedAPD plugin: ldap_domain_wblist. But we don't have any interface to manage per-domain wblist.
How to enable iRedAPD plugin ldap_domain_wblist:
*) Please test it on testing server first, it's not recommend to test it on production server directly.
*) Enable this plugin in iRedAPD config file: /opt/iredapd/etc/iredapd.ini. For example:
plugins = ldap_maillist_access_policy, ldap_domain_wblist
*) Restart iRedAPD service.
You can now store per-domain wblist on LDAP domain object with attributes:
Format is the same as per-user white/blacklist. Screenshot attached for your reference: