diff --git a/app/models/box/message_threads_extensions.rb b/app/models/box/message_threads_extensions.rb
index 0e8f6a0eb..f7d38176a 100644
--- a/app/models/box/message_threads_extensions.rb
+++ b/app/models/box/message_threads_extensions.rb
@@ -21,7 +21,7 @@ def find_or_create_by_merge_uuid!(folder:, merge_uuid:, title:, delivered_at:)
           delivered_at: delivered_at,
           last_message_delivered_at: delivered_at
         )
-        thread.merge_identifiers.build(uuid: merge_uuid, tenant: folder.tenant)
+        thread.merge_identifiers.build(uuid: merge_uuid, box: folder.box)
       end
 
       thread.save!
diff --git a/app/models/message_thread_merge_identifier.rb b/app/models/message_thread_merge_identifier.rb
index 0b856ee9f..87b273e7f 100644
--- a/app/models/message_thread_merge_identifier.rb
+++ b/app/models/message_thread_merge_identifier.rb
@@ -4,12 +4,12 @@
 #
 #  id                                          :integer          not null, primary key
 #  message_thread_id                           :integer          not null
-#  tenant_id                                   :integer          not null
+#  box_id                                      :integer          not null
 #  uuid                                        :uuid             not null
 #  created_at                                  :datetime         not null
 #  updated_at                                  :datetime         not null
 
 class MessageThreadMergeIdentifier < ApplicationRecord
   belongs_to :message_thread
-  belongs_to :tenant
+  belongs_to :box
 end
diff --git a/db/migrate/20231114132619_add_box_id_to_message_thread_merge_identifiers.rb b/db/migrate/20231114132619_add_box_id_to_message_thread_merge_identifiers.rb
new file mode 100644
index 000000000..ce1ad5602
--- /dev/null
+++ b/db/migrate/20231114132619_add_box_id_to_message_thread_merge_identifiers.rb
@@ -0,0 +1,14 @@
+class AddBoxIdToMessageThreadMergeIdentifiers < ActiveRecord::Migration[7.0]
+  def change
+    add_reference :message_thread_merge_identifiers, :box, null: true, index: true
+
+    MessageThreadMergeIdentifier.find_each do |merge_identifier|
+      merge_identifier.update(box: merge_identifier.message_thread.box)
+    end
+
+    change_column_null :message_thread_merge_identifiers, :box_id, false
+    remove_column :message_thread_merge_identifiers, :tenant_id
+
+    add_index :message_thread_merge_identifiers, [:uuid, :box_id], unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 4c939b829..f93c6d03e 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_11_01_181535) do
+ActiveRecord::Schema[7.0].define(version: 2023_11_14_132619) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -297,10 +297,10 @@
     t.uuid "uuid", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.bigint "tenant_id", null: false
+    t.bigint "box_id", null: false
+    t.index ["box_id"], name: "index_message_thread_merge_identifiers_on_box_id"
     t.index ["message_thread_id"], name: "index_message_thread_merge_identifiers_on_message_thread_id"
-    t.index ["tenant_id"], name: "index_message_thread_merge_identifiers_on_tenant_id"
-    t.index ["uuid", "tenant_id"], name: "index_message_thread_merge_identifiers_on_uuid_and_tenant_id", unique: true
+    t.index ["uuid", "box_id"], name: "index_message_thread_merge_identifiers_on_uuid_and_box_id", unique: true
   end
 
   create_table "message_thread_notes", force: :cascade do |t|
@@ -468,7 +468,6 @@
   add_foreign_key "message_relations", "messages"
   add_foreign_key "message_relations", "messages", column: "related_message_id"
   add_foreign_key "message_thread_merge_identifiers", "message_threads"
-  add_foreign_key "message_thread_merge_identifiers", "tenants"
   add_foreign_key "message_thread_notes", "message_threads"
   add_foreign_key "message_threads", "folders"
   add_foreign_key "message_threads_tags", "message_threads"
diff --git a/test/fixtures/message_thread_merge_identifiers.yml b/test/fixtures/message_thread_merge_identifiers.yml
index c1f7262d7..3af4a2304 100644
--- a/test/fixtures/message_thread_merge_identifiers.yml
+++ b/test/fixtures/message_thread_merge_identifiers.yml
@@ -3,14 +3,14 @@
 one:
   message_thread: one
   uuid: <%= SecureRandom.uuid %>
-  tenant: solver
+  box: one
 
 two:
   message_thread: one
   uuid: <%= SecureRandom.uuid %>
-  tenant: solver
+  box: one
 
 three:
   message_thread: two
   uuid: <%= SecureRandom.uuid %>
-  tenant: solver
+  box: one