diff --git a/mail_template_substitute/README.rst b/mail_template_substitute/README.rst
index 3421c57b1..9227fe5d8 100644
--- a/mail_template_substitute/README.rst
+++ b/mail_template_substitute/README.rst
@@ -14,14 +14,14 @@ Mail Template Substitute
     :target: http://www.gnu.org/licenses/agpl-3.0-standalone.html
     :alt: License: AGPL-3
 .. |badge3| image:: https://img.shields.io/badge/github-OCA%2Fsocial-lightgray.png?logo=github
-    :target: https://github.com/OCA/social/tree/12.0/mail_template_substitute
+    :target: https://github.com/OCA/social/tree/16.0/mail_template_substitute
     :alt: OCA/social
 .. |badge4| image:: https://img.shields.io/badge/weblate-Translate%20me-F47D42.png
-    :target: https://translation.odoo-community.org/projects/social-12-0/social-12-0-mail_template_substitute
+    :target: https://translation.odoo-community.org/projects/social-16-0/social-16-0-mail_template_substitute
     :alt: Translate me on Weblate
-.. |badge5| image:: https://img.shields.io/badge/runbot-Try%20me-875A7B.png
-    :target: https://runbot.odoo-community.org/runbot/205/12.0
-    :alt: Try me on Runbot
+.. |badge5| image:: https://img.shields.io/badge/runboat-Try%20me-875A7B.png
+    :target: https://runboat.odoo-community.org/webui/builds.html?repo=OCA/social&target_branch=16.0
+    :alt: Try me on Runboat
 
 |badge1| |badge2| |badge3| |badge4| |badge5| 
 
@@ -56,7 +56,7 @@ Bug Tracker
 Bugs are tracked on `GitHub Issues <https://github.com/OCA/social/issues>`_.
 In case of trouble, please check there if your issue has already been reported.
 If you spotted it first, help us smashing it by providing a detailed and welcomed
-`feedback <https://github.com/OCA/social/issues/new?body=module:%20mail_template_substitute%0Aversion:%2012.0%0A%0A**Steps%20to%20reproduce**%0A-%20...%0A%0A**Current%20behavior**%0A%0A**Expected%20behavior**>`_.
+`feedback <https://github.com/OCA/social/issues/new?body=module:%20mail_template_substitute%0Aversion:%2016.0%0A%0A**Steps%20to%20reproduce**%0A-%20...%0A%0A**Current%20behavior**%0A%0A**Expected%20behavior**>`_.
 
 Do not contact contributors directly about support or help with technical issues.
 
@@ -72,6 +72,7 @@ Contributors
 ~~~~~~~~~~~~
 
 * Bejaoui Souheil <souheil.bejaoui@acsone.eu>
+* Karthik <karthik@sodexis.com>
 
 Maintainers
 ~~~~~~~~~~~
@@ -86,6 +87,6 @@ OCA, or the Odoo Community Association, is a nonprofit organization whose
 mission is to support the collaborative development of Odoo features and
 promote its widespread use.
 
-This module is part of the `OCA/social <https://github.com/OCA/social/tree/12.0/mail_template_substitute>`_ project on GitHub.
+This module is part of the `OCA/social <https://github.com/OCA/social/tree/16.0/mail_template_substitute>`_ project on GitHub.
 
 You are welcome to contribute. To learn how please visit https://odoo-community.org/page/Contribute.
diff --git a/mail_template_substitute/__init__.py b/mail_template_substitute/__init__.py
index 1c15bc7ee..aee8895e7 100644
--- a/mail_template_substitute/__init__.py
+++ b/mail_template_substitute/__init__.py
@@ -1,3 +1,2 @@
 from . import models
 from . import wizards
-from . import tests
diff --git a/mail_template_substitute/__manifest__.py b/mail_template_substitute/__manifest__.py
index fe33d0936..b6ab9b9a3 100644
--- a/mail_template_substitute/__manifest__.py
+++ b/mail_template_substitute/__manifest__.py
@@ -6,7 +6,7 @@
     "summary": """
         This module allows to create substitution rules for mail templates.
         """,
-    "version": "12.0.1.0.1",
+    "version": "16.0.1.0.0",
     "license": "AGPL-3",
     "author": "ACSONE SA/NV," "Odoo Community Association (OCA)",
     "website": "https://github.com/OCA/social",
diff --git a/mail_template_substitute/i18n/mail_template_substitute.pot b/mail_template_substitute/i18n/mail_template_substitute.pot
index da3ee1976..a6245bf68 100644
--- a/mail_template_substitute/i18n/mail_template_substitute.pot
+++ b/mail_template_substitute/i18n/mail_template_substitute.pot
@@ -4,7 +4,7 @@
 #
 msgid ""
 msgstr ""
-"Project-Id-Version: Odoo Server 12.0\n"
+"Project-Id-Version: Odoo Server 16.0\n"
 "Report-Msgid-Bugs-To: \n"
 "Last-Translator: <>\n"
 "Language-Team: \n"
diff --git a/mail_template_substitute/models/mail_template.py b/mail_template_substitute/models/mail_template.py
index 109fc2605..ddc598dc6 100644
--- a/mail_template_substitute/models/mail_template.py
+++ b/mail_template_substitute/models/mail_template.py
@@ -1,13 +1,11 @@
 # Copyright 2019 ACSONE SA/NV
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
 
-from odoo import api, fields, models
-from odoo.tools import pycompat
+from odoo import fields, models
 from odoo.tools.safe_eval import safe_eval
 
 
 class MailTemplate(models.Model):
-
     _inherit = "mail.template"
 
     mail_template_substitution_rule_ids = fields.One2many(
@@ -16,12 +14,11 @@ class MailTemplate(models.Model):
         string="Substitution Rules",
     )
 
-    @api.multi
     def _get_substitution_template(self, model_id, active_ids):
         self.ensure_one()
-        if isinstance(active_ids, pycompat.integer_types):
+        if isinstance(active_ids, int):
             active_ids = [active_ids]
-        model = self.env[model_id.model]
+        model = self.env[model_id.sudo().model]
         for substitution_template_rule in self.mail_template_substitution_rule_ids:
             domain = safe_eval(substitution_template_rule.domain)
             domain.append(("id", "in", active_ids))
@@ -29,9 +26,8 @@ class MailTemplate(models.Model):
                 return substitution_template_rule.substitution_mail_template_id
         return False
 
-    @api.multi
-    def get_email_template(self, res_ids):
+    def _classify_per_lang(self, res_ids, engine="inline_template"):
         substitution_template = self._get_substitution_template(self.model_id, res_ids)
         if substitution_template:
-            return substitution_template.get_email_template(res_ids)
-        return super().get_email_template(res_ids)
+            return substitution_template._classify_per_lang(res_ids, engine=engine)
+        return super()._classify_per_lang(res_ids, engine=engine)
diff --git a/mail_template_substitute/models/mail_template_substitution_rule.py b/mail_template_substitute/models/mail_template_substitution_rule.py
index 0670493e6..02d92be58 100644
--- a/mail_template_substitute/models/mail_template_substitution_rule.py
+++ b/mail_template_substitute/models/mail_template_substitution_rule.py
@@ -15,7 +15,7 @@ class MailTemplateSubstitutionRule(models.Model):
         comodel_name="mail.template", required=True, ondelete="cascade"
     )
     model = fields.Char(related="mail_template_id.model_id.model", store=True)
-    domain = fields.Char(string="Domain", required=True, default="[]")
+    domain = fields.Char(required=True, default="[]")
     substitution_mail_template_id = fields.Many2one(
         comodel_name="mail.template",
         required=True,
diff --git a/mail_template_substitute/readme/CONTRIBUTORS.rst b/mail_template_substitute/readme/CONTRIBUTORS.rst
index 35c03ffe0..5b0a4d9eb 100644
--- a/mail_template_substitute/readme/CONTRIBUTORS.rst
+++ b/mail_template_substitute/readme/CONTRIBUTORS.rst
@@ -1 +1,2 @@
 * Bejaoui Souheil <souheil.bejaoui@acsone.eu>
+* Karthik <karthik@sodexis.com>
diff --git a/mail_template_substitute/static/description/index.html b/mail_template_substitute/static/description/index.html
index 5d8c4311a..4c7bc50f3 100644
--- a/mail_template_substitute/static/description/index.html
+++ b/mail_template_substitute/static/description/index.html
@@ -3,7 +3,7 @@
 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
-<meta name="generator" content="Docutils 0.15.1: http://docutils.sourceforge.net/" />
+<meta name="generator" content="Docutils: http://docutils.sourceforge.net/" />
 <title>Mail Template Substitute</title>
 <style type="text/css">
 
@@ -367,7 +367,7 @@ ul.auto-toc {
 !! This file is generated by oca-gen-addon-readme !!
 !! changes will be overwritten.                   !!
 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
-<p><a class="reference external" href="https://odoo-community.org/page/development-status"><img alt="Beta" src="https://img.shields.io/badge/maturity-Beta-yellow.png" /></a> <a class="reference external" href="http://www.gnu.org/licenses/agpl-3.0-standalone.html"><img alt="License: AGPL-3" src="https://img.shields.io/badge/licence-AGPL--3-blue.png" /></a> <a class="reference external" href="https://github.com/OCA/social/tree/12.0/mail_template_substitute"><img alt="OCA/social" src="https://img.shields.io/badge/github-OCA%2Fsocial-lightgray.png?logo=github" /></a> <a class="reference external" href="https://translation.odoo-community.org/projects/social-12-0/social-12-0-mail_template_substitute"><img alt="Translate me on Weblate" src="https://img.shields.io/badge/weblate-Translate%20me-F47D42.png" /></a> <a class="reference external" href="https://runbot.odoo-community.org/runbot/205/12.0"><img alt="Try me on Runbot" src="https://img.shields.io/badge/runbot-Try%20me-875A7B.png" /></a></p>
+<p><a class="reference external" href="https://odoo-community.org/page/development-status"><img alt="Beta" src="https://img.shields.io/badge/maturity-Beta-yellow.png" /></a> <a class="reference external" href="http://www.gnu.org/licenses/agpl-3.0-standalone.html"><img alt="License: AGPL-3" src="https://img.shields.io/badge/licence-AGPL--3-blue.png" /></a> <a class="reference external" href="https://github.com/OCA/social/tree/16.0/mail_template_substitute"><img alt="OCA/social" src="https://img.shields.io/badge/github-OCA%2Fsocial-lightgray.png?logo=github" /></a> <a class="reference external" href="https://translation.odoo-community.org/projects/social-16-0/social-16-0-mail_template_substitute"><img alt="Translate me on Weblate" src="https://img.shields.io/badge/weblate-Translate%20me-F47D42.png" /></a> <a class="reference external" href="https://runboat.odoo-community.org/webui/builds.html?repo=OCA/social&amp;target_branch=16.0"><img alt="Try me on Runboat" src="https://img.shields.io/badge/runboat-Try%20me-875A7B.png" /></a></p>
 <p>This module allows you to create substitution rules for mail templates.
 A typical use case is to replace a standard template by alternative templates
 when some conditions are met. For instance, it allows to configure alternate
@@ -401,7 +401,7 @@ templates for different companies.</p>
 <p>Bugs are tracked on <a class="reference external" href="https://github.com/OCA/social/issues">GitHub Issues</a>.
 In case of trouble, please check there if your issue has already been reported.
 If you spotted it first, help us smashing it by providing a detailed and welcomed
-<a class="reference external" href="https://github.com/OCA/social/issues/new?body=module:%20mail_template_substitute%0Aversion:%2012.0%0A%0A**Steps%20to%20reproduce**%0A-%20...%0A%0A**Current%20behavior**%0A%0A**Expected%20behavior**">feedback</a>.</p>
+<a class="reference external" href="https://github.com/OCA/social/issues/new?body=module:%20mail_template_substitute%0Aversion:%2016.0%0A%0A**Steps%20to%20reproduce**%0A-%20...%0A%0A**Current%20behavior**%0A%0A**Expected%20behavior**">feedback</a>.</p>
 <p>Do not contact contributors directly about support or help with technical issues.</p>
 </div>
 <div class="section" id="credits">
@@ -416,6 +416,7 @@ If you spotted it first, help us smashing it by providing a detailed and welcome
 <h2><a class="toc-backref" href="#id5">Contributors</a></h2>
 <ul class="simple">
 <li>Bejaoui Souheil &lt;<a class="reference external" href="mailto:souheil.bejaoui&#64;acsone.eu">souheil.bejaoui&#64;acsone.eu</a>&gt;</li>
+<li>Karthik &lt;<a class="reference external" href="mailto:karthik&#64;sodexis.com">karthik&#64;sodexis.com</a>&gt;</li>
 </ul>
 </div>
 <div class="section" id="maintainers">
@@ -425,7 +426,7 @@ If you spotted it first, help us smashing it by providing a detailed and welcome
 <p>OCA, or the Odoo Community Association, is a nonprofit organization whose
 mission is to support the collaborative development of Odoo features and
 promote its widespread use.</p>
-<p>This module is part of the <a class="reference external" href="https://github.com/OCA/social/tree/12.0/mail_template_substitute">OCA/social</a> project on GitHub.</p>
+<p>This module is part of the <a class="reference external" href="https://github.com/OCA/social/tree/16.0/mail_template_substitute">OCA/social</a> project on GitHub.</p>
 <p>You are welcome to contribute. To learn how please visit <a class="reference external" href="https://odoo-community.org/page/Contribute">https://odoo-community.org/page/Contribute</a>.</p>
 </div>
 </div>
diff --git a/mail_template_substitute/tests/test_mail_template_substitute.py b/mail_template_substitute/tests/test_mail_template_substitute.py
index 22de93c10..03c78665c 100644
--- a/mail_template_substitute/tests/test_mail_template_substitute.py
+++ b/mail_template_substitute/tests/test_mail_template_substitute.py
@@ -1,7 +1,7 @@
 # Copyright 2019 ACSONE SA/NV
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
 
-from odoo.tests.common import TransactionCase
+from odoo.tests.common import Form, TransactionCase
 
 
 class TestMailTemplateSubstitute(TransactionCase):
@@ -42,16 +42,35 @@ class TestMailTemplateSubstitute(TransactionCase):
             {"template_id": self.mt.id, "composition_mode": "mass_mail"}
         )
         self.partners = self.env["res.partner"].search([])
+        self.partner = self.env["res.partner"].search([], limit=1)
 
-    def test_get_email_template(self):
+    def test_get_email_template_partners(self):
         self.assertEqual(
             self.mt._get_substitution_template(
                 self.env.ref("base.model_res_partner"), self.partners.ids
             ),
             self.smt1,
         )
+        res_ids_to_templates = self.mt._classify_per_lang(self.partners.ids)
+        self.assertTrue(len(res_ids_to_templates))
+        _lang, (template, _res_ids) = list(res_ids_to_templates.items())[0]
         self.assertEqual(
-            self.mt.get_email_template(self.partners.ids).get(self.partners.ids[0]),
+            template,
+            self.smt1,
+        )
+
+    def test_get_email_template_partner(self):
+        self.assertEqual(
+            self.mt._get_substitution_template(
+                self.env.ref("base.model_res_partner"), self.partner.id
+            ),
+            self.smt1,
+        )
+        res_ids_to_templates = self.mt._classify_per_lang(self.partner.ids)
+        self.assertTrue(len(res_ids_to_templates))
+        _lang, (template, _res_ids) = list(res_ids_to_templates.items())[0]
+        self.assertEqual(
+            template,
             self.smt1,
         )
 
@@ -70,3 +89,15 @@ class TestMailTemplateSubstitute(TransactionCase):
             active_ids=self.partners.ids
         ).onchange_template_id_wrapper()
         self.assertEqual(self.mail_compose.template_id, self.smt2)
+
+    def test_default_get(self):
+        mail_compose_form = Form(
+            self.env["mail.compose.message"].with_context(
+                **{
+                    "default_template_id": self.mt.id,
+                    "default_model": self.partner._name,
+                    "default_res_id": self.partner.id,
+                }
+            )
+        )
+        self.assertEqual(mail_compose_form.template_id, self.smt1)
diff --git a/mail_template_substitute/wizards/mail_compose_message.py b/mail_template_substitute/wizards/mail_compose_message.py
index 65bae135e..ce31e63c3 100644
--- a/mail_template_substitute/wizards/mail_compose_message.py
+++ b/mail_template_substitute/wizards/mail_compose_message.py
@@ -13,9 +13,10 @@ class MailComposeMessage(models.TransientModel):
         if template:
             if composition_mode == "mass_mail" and self.env.context.get("active_ids"):
                 res_ids = self.env.context.get("active_ids")
-            res_ids_to_templates = template.get_email_template(res_ids)
-            if res_ids_to_templates:
-                return list(res_ids_to_templates.values())[0]
+            res_ids_to_templates = template._classify_per_lang(res_ids)
+            if len(res_ids_to_templates):
+                _lang, (template, _res_ids) = list(res_ids_to_templates.items())[0]
+                return template
         return False
 
     @api.model
@@ -30,7 +31,6 @@ class MailComposeMessage(models.TransientModel):
             result["template_id"] = substitution_template.id
         return result
 
-    @api.multi
     @api.onchange("template_id")
     def onchange_template_id_wrapper(self):
         substitution_template = self._get_substitution_template(