how to change Milboxer database schema to separate from application core db

i would like to use different database for mailboxer tables. i have a user model that acts_as_messageable but then all the mailboxer models connect to my production schema. what i have tried is using delegated model user_ex that connect to second database and set this model to acts_as_messageable but only this model connect to the secont database and all other mailboxer models connected to the production.

the code:

user.rb

class User < ActiveRecord::Base

has_one :user_ex

end

messageable_base.rb

class MessageableBase < ActiveRecord::Base

establish_connection :DB_2
self.abstract_class = true
acts_as_messageable

end

user_ex.rb

class UserEx < MessageableBase

self.table_name = 'users'
belongs_to :user

end