diff --git a/addons/test_mail/tests/test_mail_followers.py b/addons/test_mail/tests/test_mail_followers.py
index a59ef9cea3c..3d2600facce 100644
--- a/addons/test_mail/tests/test_mail_followers.py
+++ b/addons/test_mail/tests/test_mail_followers.py
@@ -91,7 +91,21 @@ class BaseFollowersTest(common.BaseFunctionalTest):
         test_record.message_subscribe(partner_ids=[self.user_admin.partner_id.id], subtype_ids=[self.mt_mg_nodef.id, self.mt_al_nodef.id])
         self.assertEqual(test_record.message_partner_ids, self.user_admin.partner_id)
         self.assertEqual(test_record.message_channel_ids, self.env['mail.channel'])
-        self.assertEqual(test_record.message_follower_ids.filtered(lambda fol: fol.partner_id == self.user_admin.partner_id).subtype_ids, self.mt_mg_nodef | self.mt_al_nodef)
+        self.assertEqual(test_record.message_follower_ids.subtype_ids, self.mt_mg_nodef | self.mt_al_nodef)
+
+    def test_followers_multiple_subscription_noforce(self):
+        test_record = self.test_record.sudo(self.user_employee)
+
+        test_record.message_subscribe(partner_ids=[self.user_admin.partner_id.id], subtype_ids=[self.mt_mg_nodef.id, self.mt_al_nodef.id])
+        self.assertEqual(test_record.message_partner_ids, self.user_admin.partner_id)
+        self.assertEqual(test_record.message_channel_ids, self.env['mail.channel'])
+        self.assertEqual(test_record.message_follower_ids.subtype_ids, self.mt_mg_nodef | self.mt_al_nodef)
+
+        # set new subtypes with force=False, meaning no rewriting of the subscription is done -> result should not change
+        test_record.message_subscribe(partner_ids=[self.user_admin.partner_id.id], force=False)
+        self.assertEqual(test_record.message_partner_ids, self.user_admin.partner_id)
+        self.assertEqual(test_record.message_channel_ids, self.env['mail.channel'])
+        self.assertEqual(test_record.message_follower_ids.subtype_ids, self.mt_mg_nodef | self.mt_al_nodef)
 
     def test_followers_no_DID(self):
         """Test that a follower cannot suffer from dissociative identity disorder.
diff --git a/addons/test_mail/tests/test_performance.py b/addons/test_mail/tests/test_performance.py
index 8432cf54993..a544b447422 100644
--- a/addons/test_mail/tests/test_performance.py
+++ b/addons/test_mail/tests/test_performance.py
@@ -192,6 +192,10 @@ class TestHeavyMailPerformance(TransactionCase):
         self.env['ir.config_parameter'].sudo().set_param('mail.catchall.alias', 'test-catchall')
         self.env['ir.config_parameter'].sudo().set_param('mail.bounce.alias', 'test-bounce')
 
+        self.channel = self.env['mail.channel'].with_context(self._quick_create_ctx).create({
+            'name': 'Listener',
+        })
+
         # prepare recipients to test for more realistic workload
         self.customer = self.env['res.partner'].with_context(self._quick_create_ctx).create({
             'name': 'Test Customer',
@@ -266,6 +270,59 @@ class TestHeavyMailPerformance(TransactionCase):
         self.assertEqual(record.message_ids[0].body, '<p>Adding stuff on %s</p>' % record.name)
         self.assertEqual(record.message_ids[0].needaction_partner_ids, self.partners | self.user_portal.partner_id | self.customer)
 
+    @mute_logger('odoo.tests', 'odoo.addons.mail.models.mail_mail', 'odoo.models.unlink')
+    @users('admin', 'emp')
+    @warmup
+    def test_complex_message_subscribe(self):
+        pids = self.partners.ids
+        cids = self.channel.ids
+        subtypes = self.env.ref('mail.mt_comment') | self.env.ref('test_mail.st_mail_test_full_umbrella_upd')
+        subtype_ids = subtypes.ids
+        rec = self.env['mail.test.full'].create({
+            'name': 'Test',
+            'umbrella_id': False,
+            'customer_id': False,
+            'user_id': self.user_portal.id,
+        })
+
+        self.assertEqual(rec.message_partner_ids, self.env.user.partner_id | self.user_portal.partner_id)
+        self.assertEqual(rec.message_channel_ids, self.env['mail.channel'])
+
+        # subscribe new followers with forced given subtypes
+        with self.assertQueryCount(admin=20, emp=21):  # test_mail only: 20 - 21
+            rec.message_subscribe(
+                partner_ids=pids[:4],
+                channel_ids=cids,
+                subtype_ids=subtype_ids,
+            )
+
+        self.assertEqual(rec.message_partner_ids, self.env.user.partner_id | self.user_portal.partner_id | self.partners[:4])
+        self.assertEqual(rec.message_channel_ids, self.channel)
+
+        # subscribe existing and new followers with force=False, meaning only some new followers will be added
+        with self.assertQueryCount(admin=11, emp=12):  # test_mail only: 11 - 12
+            rec.message_subscribe(
+                partner_ids=pids[:6],
+                channel_ids=cids,
+                subtype_ids=None,
+                force=False,
+            )
+
+        self.assertEqual(rec.message_partner_ids, self.env.user.partner_id | self.user_portal.partner_id | self.partners[:6])
+        self.assertEqual(rec.message_channel_ids, self.channel)
+
+        # subscribe existing and new followers with force=True, meaning all will have the same subtypes
+        with self.assertQueryCount(admin=48, emp=49):  # test_mail only: 48 - 49
+            rec.message_subscribe(
+                partner_ids=pids,
+                channel_ids=cids,
+                subtype_ids=subtype_ids,
+                force=True,
+            )
+
+        self.assertEqual(rec.message_partner_ids, self.env.user.partner_id | self.user_portal.partner_id | self.partners)
+        self.assertEqual(rec.message_channel_ids, self.channel)
+
     @mute_logger('odoo.tests', 'odoo.addons.mail.models.mail_mail', 'odoo.models.unlink')
     @users('admin', 'emp')
     @warmup