diff --git a/addons/test_mass_mailing/tests/__init__.py b/addons/test_mass_mailing/tests/__init__.py
index 2391896e3e4..978ceb47d01 100644
--- a/addons/test_mass_mailing/tests/__init__.py
+++ b/addons/test_mass_mailing/tests/__init__.py
@@ -5,6 +5,6 @@ from . import test_blacklist
 from . import test_blacklist_behavior
 from . import test_blacklist_mixin
 from . import test_link_tracker
-from . import test_mailing_internals
-from . import test_mass_mailing
+from . import test_mailing_test
+from . import test_mailing
 from . import test_performance
diff --git a/addons/test_mass_mailing/tests/common.py b/addons/test_mass_mailing/tests/common.py
index 43b1ad27ea1..ff368bf59be 100644
--- a/addons/test_mass_mailing/tests/common.py
+++ b/addons/test_mass_mailing/tests/common.py
@@ -11,6 +11,13 @@ class TestMassMailCommon(MassMailCommon, TestMailCommon):
     def setUpClass(cls):
         super(TestMassMailCommon, cls).setUpClass()
 
+        cls.test_alias = cls.env['mail.alias'].create({
+            'alias_name': 'test.alias',
+            'alias_user_id': False,
+            'alias_model_id': cls.env['ir.model']._get('mailing.test.simple').id,
+            'alias_contact': 'everyone'
+        })
+
         # enforce last update by user_marketing to match _process_mass_mailing_queue
         # taking last writer as user running a batch
         cls.mailing_bl = cls.env['mailing.mailing'].with_user(cls.user_marketing).create({
@@ -32,6 +39,7 @@ class TestMassMailCommon(MassMailCommon, TestMailCommon):
 </div>""",
             'mailing_type': 'mail',
             'mailing_model_id': cls.env['ir.model']._get('mailing.test.blacklist').id,
+            'reply_to_mode': 'thread',
         })
 
     @classmethod
diff --git a/addons/test_mass_mailing/tests/test_mass_mailing.py b/addons/test_mass_mailing/tests/test_mailing.py
similarity index 63%
rename from addons/test_mass_mailing/tests/test_mass_mailing.py
rename to addons/test_mass_mailing/tests/test_mailing.py
index 0a2f45f0e17..4179327de94 100644
--- a/addons/test_mass_mailing/tests/test_mass_mailing.py
+++ b/addons/test_mass_mailing/tests/test_mailing.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+from odoo.addons.test_mass_mailing.data.mail_test_data import MAIL_TEMPLATE
 from odoo.addons.test_mass_mailing.tests.common import TestMassMailCommon
 from odoo.tests import tagged
 from odoo.tests.common import users
@@ -14,6 +15,62 @@ class TestMassMailing(TestMassMailCommon):
     def setUpClass(cls):
         super(TestMassMailing, cls).setUpClass()
 
+    @users('user_marketing')
+    @mute_logger('odoo.addons.mail.models.mail_thread')
+    def test_mailing_gateway_reply(self):
+        customers = self.env['res.partner']
+        for x in range(0, 3):
+            customers |= self.env['res.partner'].create({
+                'name': 'Customer_%02d' % x,
+                'email': '"Customer_%02d" <customer_%02d@test.example.com' % (x, x),
+            })
+
+        mailing = self.env['mailing.mailing'].create({
+            'name': 'TestName',
+            'subject': 'TestSubject',
+            'body_html': 'Hello ${object.name}',
+            'reply_to_mode': 'email',
+            'reply_to': '%s@%s' % (self.test_alias.alias_name, self.test_alias.alias_domain),
+            'keep_archives': True,
+            'mailing_model_id': self.env['ir.model']._get('res.partner').id,
+            'mailing_domain': '%s' % [('id', 'in', customers.ids)],
+        })
+        mailing.action_put_in_queue()
+        with self.mock_mail_gateway(mail_unlink_sent=False):
+            mailing.action_send_mail()
+
+        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, customers[0], use_in_reply_to=True)
+        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, customers[1], use_in_reply_to=False)
+
+        # customer2 looses headers
+        mail_mail = self._find_mail_mail_wrecord(customers[2])
+        self.format_and_process(
+            MAIL_TEMPLATE,
+            mail_mail.email_to,
+            mail_mail.reply_to,
+            subject='Re: %s' % mail_mail.subject,
+            extra='',
+            msg_id='<123456.%s.%d@test.example.com>' % (customers[2]._name, customers[2].id),
+            target_model=customers[2]._name, target_field=customers[2]._rec_name,
+        )
+        mailing.flush()
+
+        # check traces status
+        traces = self.env['mailing.trace'].search([('model', '=', customers._name), ('res_id', 'in', customers.ids)])
+        self.assertEqual(len(traces), 3)
+        customer0_trace = traces.filtered(lambda t: t.res_id == customers[0].id)
+        self.assertEqual(customer0_trace.state, 'replied')
+        customer1_trace = traces.filtered(lambda t: t.res_id == customers[1].id)
+        self.assertEqual(customer1_trace.state, 'replied')
+        customer2_trace = traces.filtered(lambda t: t.res_id == customers[2].id)
+        self.assertEqual(customer2_trace.state, 'sent')
+
+        # check mailing statistics
+        self.assertEqual(mailing.sent, 3)
+        self.assertEqual(mailing.delivered, 3)
+        self.assertEqual(mailing.opened, 2)
+        self.assertEqual(mailing.replied, 2)
+
     @users('user_marketing')
     @mute_logger('odoo.addons.mail.models.mail_mail')
     def test_mailing_gateway_update(self):
@@ -62,6 +119,52 @@ class TestMassMailing(TestMassMailCommon):
         self.assertMailingStatistics(mailing, expected=5, delivered=4, sent=5, opened=1, clicked=1, bounced=1)
         self.assertEqual(recipients[1].message_bounce, 1)
 
+    @users('user_marketing')
+    @mute_logger('odoo.addons.mail.models.mail_thread')
+    def test_mailing_trace_utm(self):
+        """ Test mailing UTMs are caught on reply"""
+        self._create_mailing_list()
+        self.test_alias.write({
+            'alias_model_id': self.env['ir.model']._get('mailing.test.utm').id
+        })
+
+        source = self.env['utm.source'].create({'name': 'Source test'})
+        medium = self.env['utm.medium'].create({'name': 'Medium test'})
+        campaign = self.env['utm.campaign'].create({'name': 'Campaign test'})
+        subject = 'MassMailingTestUTM'
+
+        mailing = self.env['mailing.mailing'].create({
+            'name': 'UTMTest',
+            'subject': subject,
+            'body_html': '<p>Hello ${object.name}</p>',
+            'reply_to_mode': 'email',
+            'reply_to': '%s@%s' % (self.test_alias.alias_name, self.test_alias.alias_domain),
+            'keep_archives': True,
+            'mailing_model_id': self.env['ir.model']._get('mailing.list').id,
+            'contact_list_ids': [(4, self.mailing_list_1.id)],
+            'source_id': source.id,
+            'medium_id': medium.id,
+            'campaign_id': campaign.id
+        })
+
+        mailing.action_put_in_queue()
+        with self.mock_mail_gateway(mail_unlink_sent=False):
+            mailing._process_mass_mailing_queue()
+
+        traces = self.env['mailing.trace'].search([('model', '=', self.mailing_list_1.contact_ids._name), ('res_id', 'in', self.mailing_list_1.contact_ids.ids)])
+        self.assertEqual(len(traces), 3)
+
+        # simulate response to mailing
+        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, self.mailing_list_1.contact_ids[0], use_in_reply_to=True)
+        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, self.mailing_list_1.contact_ids[1], use_in_reply_to=False)
+
+        mailing_test_utms = self.env['mailing.test.utm'].search([('name', '=', 'Re: %s' % subject)])
+        self.assertEqual(len(mailing_test_utms), 2)
+        for test_utm in mailing_test_utms:
+            self.assertEqual(test_utm.campaign_id, campaign)
+            self.assertEqual(test_utm.source_id, source)
+            self.assertEqual(test_utm.medium_id, medium)
+
     @users('user_marketing')
     @mute_logger('odoo.addons.mail.models.mail_mail')
     def test_mailing_w_blacklist(self):
diff --git a/addons/test_mass_mailing/tests/test_mailing_internals.py b/addons/test_mass_mailing/tests/test_mailing_internals.py
deleted file mode 100644
index 555578e492d..00000000000
--- a/addons/test_mass_mailing/tests/test_mailing_internals.py
+++ /dev/null
@@ -1,163 +0,0 @@
-# -*- coding: utf-8 -*-
-# Part of Odoo. See LICENSE file for full copyright and licensing details.
-
-from odoo.addons.test_mass_mailing.tests.common import TestMassMailCommon
-from odoo.addons.test_mass_mailing.data.mail_test_data import MAIL_TEMPLATE
-from odoo.tests.common import users
-from odoo.tools import mute_logger
-
-
-class TestMailingInternals(TestMassMailCommon):
-
-    def setUp(self):
-        super(TestMailingInternals, self).setUp()
-
-        self.env['ir.config_parameter'].set_param('mail.bounce.alias', 'bounce.test')
-        self.env['ir.config_parameter'].set_param('mail.catchall.alias', 'catchall.test')
-        self.env['ir.config_parameter'].set_param('mail.catchall.domain', 'test.example.com')
-
-        self.test_alias = self.env['mail.alias'].create({
-            'alias_name': 'test.alias',
-            'alias_user_id': False,
-            'alias_model_id': self.env['ir.model']._get('mailing.test.simple').id,
-            'alias_contact': 'everyone'
-        })
-
-    @mute_logger('odoo.addons.mail.models.mail_render_mixin')
-    def test_mailing_test_button(self):
-        mailing = self.env['mailing.mailing'].create({
-            'name': 'TestButton',
-            'subject': 'Subject ${object.name}',
-            'preview': 'Preview ${object.name}',
-            'state': 'draft',
-            'mailing_type': 'mail',
-            'body_html': '<p>Hello ${object.name}</p>',
-            'mailing_model_id': self.env['ir.model']._get('res.partner').id,
-        })
-        mailing_test = self.env['mailing.mailing.test'].create({
-            'email_to': 'test@test.com',
-            'mass_mailing_id': mailing.id,
-        })
-
-        with self.mock_mail_gateway():
-            mailing_test.send_mail_test()
-
-        # Test if bad jinja in the subject raises an error
-        mailing.write({'subject': 'Subject ${object.name_id.id}'})
-        with self.mock_mail_gateway(), self.assertRaises(Exception):
-            mailing_test.send_mail_test()
-
-        # Test if bad jinja in the body raises an error
-        mailing.write({
-            'subject': 'Subject ${object.name}',
-            'body_html': '<p>Hello ${object.name_id.id}</p>',
-        })
-        with self.mock_mail_gateway(), self.assertRaises(Exception):
-            mailing_test.send_mail_test()
-
-        # Test if bad jinja in the preview raises an error
-        mailing.write({
-            'body_html': '<p>Hello ${object.name}</p>',
-            'preview': 'Preview ${object.name_id.id}',
-        })
-        with self.mock_mail_gateway(), self.assertRaises(Exception):
-            mailing_test.send_mail_test()
-
-    def test_mailing_trace_update(self):
-        customers = self.env['res.partner']
-        for x in range(0, 3):
-            customers |= self.env['res.partner'].create({
-                'name': 'Customer_%02d' % x,
-                'email': '"Customer_%02d" <customer_%02d@test.example.com' % (x, x),
-            })
-
-        mailing = self.env['mailing.mailing'].create({
-            'name': 'TestName',
-            'subject': 'TestSubject',
-            'body_html': 'Hello ${object.name}',
-            'reply_to_mode': 'email',
-            'reply_to': '%s@%s' % (self.test_alias.alias_name, self.test_alias.alias_domain),
-            'keep_archives': True,
-            'mailing_model_id': self.env['ir.model']._get('res.partner').id,
-            'mailing_domain': '%s' % [('id', 'in', customers.ids)],
-        })
-        mailing.action_put_in_queue()
-        with self.mock_mail_gateway(mail_unlink_sent=False):
-            mailing.action_send_mail()
-
-        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, customers[0], use_in_reply_to=True)
-        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, customers[1], use_in_reply_to=False)
-
-        # customer2 looses headers
-        mail_mail = self._find_mail_mail_wrecord(customers[2])
-        self.format_and_process(
-            MAIL_TEMPLATE,
-            mail_mail.email_to,
-            mail_mail.reply_to,
-            subject='Re: %s' % mail_mail.subject,
-            extra='',
-            msg_id='<123456.%s.%d@test.example.com>' % (customers[2]._name, customers[2].id),
-            target_model=customers[2]._name, target_field=customers[2]._rec_name,
-        )
-        mailing.flush()
-
-        # check traces status
-        traces = self.env['mailing.trace'].search([('model', '=', customers._name), ('res_id', 'in', customers.ids)])
-        self.assertEqual(len(traces), 3)
-        customer0_trace = traces.filtered(lambda t: t.res_id == customers[0].id)
-        self.assertEqual(customer0_trace.state, 'replied')
-        customer1_trace = traces.filtered(lambda t: t.res_id == customers[1].id)
-        self.assertEqual(customer1_trace.state, 'replied')
-        customer2_trace = traces.filtered(lambda t: t.res_id == customers[2].id)
-        self.assertEqual(customer2_trace.state, 'sent')
-
-        # check mailing statistics
-        self.assertEqual(mailing.sent, 3)
-        self.assertEqual(mailing.delivered, 3)
-        self.assertEqual(mailing.opened, 2)
-        self.assertEqual(mailing.replied, 2)
-
-    @users('user_marketing')
-    def test_mailing_trace_utm(self):
-        """ Test mailing UTMs are caught on reply"""
-        self._create_mailing_list()
-        self.test_alias.write({
-            'alias_model_id': self.env['ir.model']._get('mailing.test.utm').id
-        })
-
-        source = self.env['utm.source'].create({'name': 'Source test'})
-        medium = self.env['utm.medium'].create({'name': 'Medium test'})
-        campaign = self.env['utm.campaign'].create({'name': 'Campaign test'})
-        subject = 'MassMailingTestUTM'
-
-        mailing = self.env['mailing.mailing'].create({
-            'name': 'UTMTest',
-            'subject': subject,
-            'body_html': '<p>Hello ${object.name}</p>',
-            'reply_to_mode': 'email',
-            'reply_to': '%s@%s' % (self.test_alias.alias_name, self.test_alias.alias_domain),
-            'keep_archives': True,
-            'mailing_model_id': self.env['ir.model']._get('mailing.list').id,
-            'contact_list_ids': [(4, self.mailing_list_1.id)],
-            'source_id': source.id,
-            'medium_id': medium.id,
-            'campaign_id': campaign.id
-        })
-
-        mailing.action_put_in_queue()
-        with self.mock_mail_gateway(mail_unlink_sent=False):
-            mailing._process_mass_mailing_queue()
-
-        traces = self.env['mailing.trace'].search([('model', '=', self.mailing_list_1.contact_ids._name), ('res_id', 'in', self.mailing_list_1.contact_ids.ids)])
-        self.assertEqual(len(traces), 3)
-
-        # simulate response to mailing
-        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, self.mailing_list_1.contact_ids[0], use_in_reply_to=True)
-        self.gateway_mail_reply_wrecord(MAIL_TEMPLATE, self.mailing_list_1.contact_ids[1], use_in_reply_to=False)
-
-        mailing_test_utms = self.env['mailing.test.utm'].search([('name', '=', 'Re: %s' % subject)])
-        self.assertEqual(len(mailing_test_utms), 2)
-        for test_utm in mailing_test_utms:
-            self.assertEqual(test_utm.campaign_id, campaign)
-            self.assertEqual(test_utm.source_id, source)
-            self.assertEqual(test_utm.medium_id, medium)
diff --git a/addons/test_mass_mailing/tests/test_mailing_test.py b/addons/test_mass_mailing/tests/test_mailing_test.py
new file mode 100644
index 00000000000..33c0419af07
--- /dev/null
+++ b/addons/test_mass_mailing/tests/test_mailing_test.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo.addons.test_mass_mailing.tests.common import TestMassMailCommon
+from odoo.tests.common import users
+from odoo.tools import mute_logger
+
+
+class TestMailingTest(TestMassMailCommon):
+
+    @users('user_marketing')
+    @mute_logger('odoo.addons.mail.models.mail_render_mixin')
+    def test_mailing_test_button(self):
+        mailing = self.env['mailing.mailing'].create({
+            'name': 'TestButton',
+            'subject': 'Subject ${object.name}',
+            'preview': 'Preview ${object.name}',
+            'state': 'draft',
+            'mailing_type': 'mail',
+            'body_html': '<p>Hello ${object.name}</p>',
+            'mailing_model_id': self.env['ir.model']._get('res.partner').id,
+        })
+        mailing_test = self.env['mailing.mailing.test'].create({
+            'email_to': 'test@test.com',
+            'mass_mailing_id': mailing.id,
+        })
+
+        with self.mock_mail_gateway():
+            mailing_test.send_mail_test()
+
+        # Test if bad jinja in the subject raises an error
+        mailing.write({'subject': 'Subject ${object.name_id.id}'})
+        with self.mock_mail_gateway(), self.assertRaises(Exception):
+            mailing_test.send_mail_test()
+
+        # Test if bad jinja in the body raises an error
+        mailing.write({
+            'subject': 'Subject ${object.name}',
+            'body_html': '<p>Hello ${object.name_id.id}</p>',
+        })
+        with self.mock_mail_gateway(), self.assertRaises(Exception):
+            mailing_test.send_mail_test()
+
+        # Test if bad jinja in the preview raises an error
+        mailing.write({
+            'body_html': '<p>Hello ${object.name}</p>',
+            'preview': 'Preview ${object.name_id.id}',
+        })
+        with self.mock_mail_gateway(), self.assertRaises(Exception):
+            mailing_test.send_mail_test()