diff --git a/addons/mail/tests/test_mail_gateway.py b/addons/mail/tests/test_mail_gateway.py
index 93d873ce0cc..70ec56fa9a6 100644
--- a/addons/mail/tests/test_mail_gateway.py
+++ b/addons/mail/tests/test_mail_gateway.py
@@ -1134,7 +1134,7 @@ class TestMailgateway(TestMail):
         self.assertEqual(msg.model, False,
                          'message_post: private discussion: context key "thread_model" not correctly ignored when having no res_id')
         # Test: message-id
-        self.assertIn('openerp-private', msg.message_id, 'message_post: private discussion: message-id should contain the private keyword')
+        self.assertIn('openerp-private', msg.message_id.split('@')[0], 'message_post: private discussion: message-id should contain the private keyword')
 
         # Do: Bert replies through mailgateway (is a customer)
         self.format_and_process(
@@ -1162,9 +1162,9 @@ class TestMailgateway(TestMail):
     @mute_logger('odoo.addons.mail.models.mail_thread', 'odoo.models', 'odoo.addons.mail.models.mail_mail')
     def test_forward_parent_id(self):
         msg = self.test_pigs.sudo(self.user_employee).message_post(no_auto_thread=True, subtype='mail.mt_comment')
-        self.assertNotIn(msg.model, msg.message_id)
-        self.assertNotIn('-%d-' % msg.res_id, msg.message_id)
-        self.assertIn('reply_to', msg.message_id)
+        self.assertNotIn(msg.model, msg.message_id.split('@')[0])
+        self.assertNotIn('-%d-' % msg.res_id, msg.message_id.split('@')[0])
+        self.assertIn('reply_to', msg.message_id.split('@')[0])
 
         # forward it to a new thread AND an existing thread
         fw_msg_id = '<THIS.IS.A.FW.MESSAGE.1@bert.fr>'
diff --git a/addons/mail/tests/test_mail_message.py b/addons/mail/tests/test_mail_message.py
index c91cc373ced..9586ccbe192 100644
--- a/addons/mail/tests/test_mail_message.py
+++ b/addons/mail/tests/test_mail_message.py
@@ -17,7 +17,7 @@ class TestMailMessage(TestMail):
             'reply_to': 'test.reply@example.com',
             'email_from': 'test.from@example.com',
         })
-        self.assertIn('-private', msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-private', msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, 'test.reply@example.com')
         self.assertEqual(msg.email_from, 'test.from@example.com')
 
@@ -25,7 +25,7 @@ class TestMailMessage(TestMail):
         self.env['ir.config_parameter'].search([('key', '=', 'mail.catchall.domain')]).unlink()
 
         msg = self.env['mail.message'].sudo(self.user_employee).create({})
-        self.assertIn('-private', msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-private', msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -35,7 +35,7 @@ class TestMailMessage(TestMail):
         self.env['ir.config_parameter'].search([('key', '=', 'mail.catchall.alias')]).unlink()
 
         msg = self.env['mail.message'].sudo(self.user_employee).create({})
-        self.assertIn('-private', msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-private', msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -46,7 +46,7 @@ class TestMailMessage(TestMail):
         self.env['ir.config_parameter'].set_param('mail.catchall.alias', alias_catchall)
 
         msg = self.env['mail.message'].sudo(self.user_employee).create({})
-        self.assertIn('-private', msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-private', msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s <%s@%s>' % (self.env.user.company_id.name, alias_catchall, alias_domain))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -57,7 +57,7 @@ class TestMailMessage(TestMail):
             'model': 'mail.test',
             'res_id': self.test_pigs.id
         })
-        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -70,7 +70,7 @@ class TestMailMessage(TestMail):
             'model': 'mail.test',
             'res_id': self.test_pigs.id
         })
-        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s %s <%s@%s>' % (self.env.user.company_id.name, self.test_pigs.name, self.test_pigs.alias_name, alias_domain))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -84,7 +84,7 @@ class TestMailMessage(TestMail):
             'model': 'mail.test',
             'res_id': self.test_pigs.id
         })
-        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id, 'mail_message: message_id for a void message should be a "private" one')
+        self.assertIn('-openerp-%d-mail.test' % self.test_pigs.id, msg.message_id.split('@')[0], 'mail_message: message_id for a void message should be a "private" one')
         self.assertEqual(msg.reply_to, '%s %s <%s@%s>' % (self.env.user.company_id.name, self.test_pigs.name, self.test_pigs.alias_name, alias_domain))
         self.assertEqual(msg.email_from, '%s <%s>' % (self.user_employee.name, self.user_employee.email))
 
@@ -94,9 +94,9 @@ class TestMailMessage(TestMail):
             'res_id': self.test_pigs.id,
             'no_auto_thread': True,
         })
-        self.assertIn('reply_to', msg.message_id)
-        self.assertNotIn('mail.test', msg.message_id)
-        self.assertNotIn('-%d-' % self.test_pigs.id, msg.message_id)
+        self.assertIn('reply_to', msg.message_id.split('@')[0])
+        self.assertNotIn('mail.test', msg.message_id.split('@')[0])
+        self.assertNotIn('-%d-' % self.test_pigs.id, msg.message_id.split('@')[0])
 
     def test_mail_message_notify_from_mail_mail(self):
         # Due ot post-commit hooks, store send emails in every step