diff --git a/addons/calendar/models/calendar_attendee.py b/addons/calendar/models/calendar_attendee.py
index 9df8051e061..0506fad587a 100644
--- a/addons/calendar/models/calendar_attendee.py
+++ b/addons/calendar/models/calendar_attendee.py
@@ -123,8 +123,7 @@ class Attendee(models.Model):
                 body = mail_template._render_field(
                     'body_html',
                     attendee.ids,
-                    compute_lang=True,
-                    post_process=True)[attendee.id]
+                    compute_lang=True)[attendee.id]
                 subject = mail_template._render_field(
                     'subject',
                     attendee.ids,
diff --git a/addons/digest/models/digest.py b/addons/digest/models/digest.py
index 735a78f4be3..354d3a7d59d 100644
--- a/addons/digest/models/digest.py
+++ b/addons/digest/models/digest.py
@@ -165,8 +165,10 @@ class Digest(models.Model):
                 'tips': self._compute_tips(user.company_id, user, tips_count=tips_count, consumed=consume_tips),
                 'preferences': self._compute_preferences(user.company_id, user),
             },
-            post_process=True,
-            options={'preserve_comments': True}
+            options={
+                'preserve_comments': True,
+                'post_process': True,
+            },
         )[self.id]
         full_mail = self.env['mail.render.mixin']._render_encapsulate(
             'digest.digest_mail_layout',
@@ -288,7 +290,15 @@ class Digest(models.Model):
             '|', ('group_id', 'in', user.groups_id.ids), ('group_id', '=', False)
         ], limit=tips_count)
         tip_descriptions = [
-            tools.html_sanitize(self.env['mail.render.mixin'].sudo()._render_template(tip.tip_description, 'digest.tip', tip.ids, post_process=True, engine="qweb")[tip.id])
+            tools.html_sanitize(
+                self.env['mail.render.mixin'].sudo()._render_template(
+                    tip.tip_description,
+                    'digest.tip',
+                    tip.ids,
+                    engine="qweb",
+                    options={'post_process': True},
+                )[tip.id]
+            )
             for tip in tips
         ]
         if consumed:
diff --git a/addons/mail/models/mail_composer_mixin.py b/addons/mail/models/mail_composer_mixin.py
index 9619eae88f8..a17b5941199 100644
--- a/addons/mail/models/mail_composer_mixin.py
+++ b/addons/mail/models/mail_composer_mixin.py
@@ -22,7 +22,9 @@ class MailComposerMixin(models.AbstractModel):
 
     # Content
     subject = fields.Char('Subject', compute='_compute_subject', readonly=False, store=True)
-    body = fields.Html('Contents', compute='_compute_body', render_engine='qweb', store=True, readonly=False, sanitize=False)
+    body = fields.Html(
+        'Contents', compute='_compute_body', readonly=False, store=True,
+        render_engine='qweb', render_options={'post_process': True}, sanitize=False)
     template_id = fields.Many2one('mail.template', 'Mail Template', domain="[('model', '=', render_model)]")
     # Access
     is_mail_template_editor = fields.Boolean('Is Editor', compute='_compute_is_mail_template_editor')
diff --git a/addons/mail/models/mail_render_mixin.py b/addons/mail/models/mail_render_mixin.py
index 8ad6fe4a913..63da0106246 100644
--- a/addons/mail/models/mail_render_mixin.py
+++ b/addons/mail/models/mail_render_mixin.py
@@ -284,12 +284,13 @@ class MailRenderMixin(models.AbstractModel):
         :param dict add_context: additional context to give to renderer. It
           allows to add or update values to base rendering context generated
           by ``MailRenderMixin._render_eval_context()``;
-        :param dict options: options for rendering (not used currently);
+        :param dict options: options for rendering propagated to IrQweb render
+          (see docstring for available options);
 
         :return dict: {res_id: string of rendered template based on record}
         """
         results = dict.fromkeys(res_ids, u"")
-        if not template_src:
+        if not template_src or not res_ids:
             return results
 
         # prepare template variables
@@ -337,15 +338,14 @@ class MailRenderMixin(models.AbstractModel):
         :param dict add_context: additional context to give to renderer. It
           allows to add or update values to base rendering context generated
           by ``MailRenderMixin._render_eval_context()``;
-        :param dict options: options for rendering (not used currently);
+        :param dict options: options for rendering propagated to IrQweb render
+          (see docstring for available options);
 
         :return dict: {res_id: string of rendered template based on record}
         """
-        # prevent wrong values (rendering on a void record set, ...)
-        if any(r is None for r in res_ids):
-            raise ValueError(_('Template rendering should be called on a valid record IDs.'))
-
         results = {}
+        if not res_ids:
+            return results
 
         # prepare template variables
         variables = self._render_eval_context()
@@ -380,16 +380,13 @@ class MailRenderMixin(models.AbstractModel):
         :param dict add_context: additional context to give to renderer. It
           allows to add or update values to base rendering context generated
           by ``MailRenderMixin._render_inline_template_eval_context()``;
-        :param dict options: options for rendering;
+        :param dict options: options for rendering (no options available
+          currently);
 
         :return dict: {res_id: string of rendered template based on record}
         """
-        # prevent wrong values (rendering on a void record set, ...)
-        if any(r is None for r in res_ids):
-            raise ValueError(_('Template rendering should be called on a valid record IDs.'))
-
         results = dict.fromkeys(res_ids, u"")
-        if not template_txt:
+        if not template_txt or not res_ids:
             return results
 
         template_instructions = parse_inline_template(str(template_txt))
@@ -440,7 +437,7 @@ class MailRenderMixin(models.AbstractModel):
 
     @api.model
     def _render_template(self, template_src, model, res_ids, engine='inline_template',
-                         add_context=None, options=None, post_process=False):
+                         add_context=None, options=None):
         """ Render the given string on records designed by model / res_ids using
         the given rendering engine. Possible engine are small_web, qweb, or
         qweb_view.
@@ -455,12 +452,20 @@ class MailRenderMixin(models.AbstractModel):
         :param dict add_context: additional context to give to renderer. It
           allows to add or update values to base rendering context generated
           by ``MailRenderMixin._render_<engine>_eval_context()``;
-        :param dict options: options for rendering;
-        :param boolean post_process: perform a post processing on rendered result
-          (notably html links management). See``_render_template_postprocess``;
+        :param dict options: options for rendering. Use in this method and also
+          propagated to rendering sub-methods. May contain notably
+
+            boolean post_process: perform a post processing on rendered result
+            (notably html links management). See``_render_template_postprocess``;
+            boolean preserve_comments: if set, comments are preserved. Default
+            behavior is to remove them. It is used notably for browser-specific
+            code implemented like comments;
 
         :return dict: {res_id: string of rendered template based on record}
         """
+        if options is None:
+            options = {}
+
         if not isinstance(res_ids, (list, tuple)):
             raise ValueError(_('Template rendering should be called only using on a list of IDs.'))
         if engine not in ('inline_template', 'qweb', 'qweb_view'):
@@ -476,7 +481,7 @@ class MailRenderMixin(models.AbstractModel):
             rendered = self._render_template_inline_template(template_src, model, res_ids,
                                                              add_context=add_context, options=options)
 
-        if post_process:
+        if options.get('post_process'):
             rendered = self._render_template_postprocess(rendered)
 
         return rendered
@@ -529,7 +534,7 @@ class MailRenderMixin(models.AbstractModel):
 
     def _render_field(self, field, res_ids, engine='inline_template',
                       compute_lang=False, set_lang=False,
-                      add_context=None, options=None, post_process=False):
+                      add_context=None, options=None):
         """ Given some record ids, render a template located on field on all
         records. ``field`` should be a field of self (i.e. ``body_html`` on
         ``mail.template``). res_ids are record IDs linked to ``model`` field
@@ -548,12 +553,25 @@ class MailRenderMixin(models.AbstractModel):
           ``compute_lang`` is False;
 
         :param dict add_context: additional context to give to renderer;
-        :param dict options: options for rendering;
-        :param boolean post_process: perform a post processing on rendered result
-          (notably html links management). See``_render_template_postprocess``);
+        :param dict options: options for rendering. Use in this method and also
+          propagated to rendering sub-methods. Base values come from the field
+          (coming from ``render_options`` parameter) and are updated by this
+          optional dictionary. May contain notably
+
+            boolean post_process: perform a post processing on rendered result
+            (notably html links management). See``_render_template_postprocess``;
+            boolean preserve_comments: if set, comments are preserved. Default
+            behavior is to remove them. It is used notably for browser-specific
+            code implemented like comments;
 
         :return dict: {res_id: string of rendered template based on record}
         """
+        if field not in self:
+            raise ValueError(
+                _('Rendering of %(field_name)s is not possible as not defined on template.',
+                  field_name=field
+                 )
+            )
         if options is None:
             options = {}
 
@@ -565,10 +583,11 @@ class MailRenderMixin(models.AbstractModel):
         else:
             templates_res_ids = {self._context.get('lang'): (self, res_ids)}
 
-        # rendering options
+        # rendering options (update default defined on field by asked options)
         engine = getattr(self._fields[field], 'render_engine', engine)
-        options.update(**getattr(self._fields[field], 'render_options', {}))
-        post_process = options.get('post_process') or post_process
+        field_options = getattr(self._fields[field], 'render_options', {})
+        if options:
+            field_options.update(**options)
 
         return dict(
             (res_id, rendered)
@@ -579,7 +598,6 @@ class MailRenderMixin(models.AbstractModel):
                 tpl_res_ids,
                 engine=engine,
                 add_context=add_context,
-                options=options,
-                post_process=post_process
+                options=field_options,
             ).items()
         )
diff --git a/addons/mail/models/mail_template.py b/addons/mail/models/mail_template.py
index 920647e98c7..7825c182cd4 100644
--- a/addons/mail/models/mail_template.py
+++ b/addons/mail/models/mail_template.py
@@ -56,7 +56,9 @@ class MailTemplate(models.Model):
     email_cc = fields.Char('Cc', help="Carbon copy recipients (placeholders may be used here)")
     reply_to = fields.Char('Reply To', help="Email address to which replies will be redirected when sending emails in mass; only used when the reply is not logged in the original discussion thread.")
     # content
-    body_html = fields.Html('Body', render_engine='qweb', translate=True, prefetch=True, sanitize=False)
+    body_html = fields.Html(
+        'Body', render_engine='qweb', render_options={'post_process': True},
+        prefetch=True, translate=True, sanitize=False)
     attachment_ids = fields.Many2many('ir.attachment', 'email_template_attachment_rel', 'email_template_id',
                                       'attachment_id', 'Attachments',
                                       help="You may attach files to this template, to be added to all "
@@ -246,8 +248,7 @@ class MailTemplate(models.Model):
         for lang, (template, template_res_ids) in self._classify_per_lang(res_ids).items():
             for field in fields:
                 generated_field_values = template._render_field(
-                    field, template_res_ids,
-                    post_process=(field == 'body_html')
+                    field, template_res_ids
                 )
                 for res_id, field_value in generated_field_values.items():
                     results.setdefault(res_id, dict())[field] = field_value
diff --git a/addons/mail/tests/common.py b/addons/mail/tests/common.py
index 3912398d5c3..675779e19e9 100644
--- a/addons/mail/tests/common.py
+++ b/addons/mail/tests/common.py
@@ -19,7 +19,7 @@ from odoo.addons.mail.models.mail_mail import MailMail
 from odoo.addons.mail.models.mail_message import Message
 from odoo.addons.mail.models.mail_notification import MailNotification
 from odoo.tests import common, new_test_user
-from odoo.tools import formataddr, pycompat
+from odoo.tools import formataddr, mute_logger, pycompat
 from odoo.tools.translate import code_translations
 
 mail_new_test_user = partial(new_test_user, context={'mail_create_nolog': True,
@@ -1102,9 +1102,9 @@ class MailCommon(common.TransactionCase, MailCase):
             * 'English Layout for' -> Spanish Layout para
           * model
             * description: English:    Lang Chatter Model (depends on test_record._name)
-                           translated: Spanish description
+                           translated: Spanish Model Description
           * module
-            * _('TestStuff') -> TestSpanishStuff (used as link button name in layout)
+            * _('NotificationButtonTitle') -> SpanishNotificationButtonTitle (used as link button name in layout)
             * _('View %s') -> SpanishView %s
           * template
             * body: English:    <p>EnglishBody for <t t-out="object.name"/></p> (depends on test_template.body)
@@ -1114,17 +1114,22 @@ class MailCommon(common.TransactionCase, MailCase):
         """
         # activate translations
         cls.env['res.lang']._activate_lang(lang_code)
-        cls.env.ref('base.module_base')._update_translations([lang_code])
+        with mute_logger("odoo.addons.base.models.ir_module", "odoo.tools.translate"):
+            cls.env.ref('base.module_base')._update_translations([lang_code])
+            cls.env.ref('base.module_mail')._update_translations([lang_code])
+            cls.env.ref('base.module_test_mail')._update_translations([lang_code])
+            code_translations.get_python_translations('mail', lang_code)
+            code_translations.get_python_translations('test_mail', lang_code)
 
         # Make sure Spanish translations have not been altered
         if test_record:
-            cls.env['ir.model']._get(test_record._name).with_context(lang=lang_code).name = 'Spanish description'
+            cls.env['ir.model']._get(test_record._name).with_context(lang=lang_code).name = 'Spanish Model Description'
 
         # Translate some code strings used in mailing
-        code_translations.python_translations[('test_mail', 'es_ES')] = {'TestStuff': 'TestSpanishStuff'}
-        cls.addClassCleanup(code_translations.python_translations.pop, ('test_mail', 'es_ES'))
-        code_translations.python_translations[('mail', 'es_ES')] = {'View %s': 'SpanishView %s'}
-        cls.addClassCleanup(code_translations.python_translations.pop, ('mail', 'es_ES'))
+        code_translations.python_translations[('test_mail', 'es_ES')]['NotificationButtonTitle'] = 'SpanishButtonTitle'
+        cls.addClassCleanup(code_translations.python_translations[('test_mail', 'es_ES')].pop, 'NotificationButtonTitle')
+        code_translations.python_translations[('mail', 'es_ES')]['View %s'] = 'SpanishView %s'
+        cls.addClassCleanup(code_translations.python_translations[('mail', 'es_ES')].pop, 'View %s')
 
         # Prepare some translated value for template if given
         if test_template:
diff --git a/addons/mail/tests/test_mail_render.py b/addons/mail/tests/test_mail_render.py
index b196063043c..b97f9a0305f 100644
--- a/addons/mail/tests/test_mail_render.py
+++ b/addons/mail/tests/test_mail_render.py
@@ -97,6 +97,13 @@ class TestMailRenderCommon(common.MailCommon):
     <span>Autre Narrateur</span>
 </p>"""
         ]
+        cls.base_rendered_void = [
+            '<p>Hello</p>',
+            '<p>Hello </p>',
+            """<p>
+    <span>English Speaker</span>
+</p>"""
+        ]
 
         # link to mail template
         cls.test_template = cls.env['mail.template'].create({
@@ -198,6 +205,43 @@ class TestMailRender(TestMailRenderCommon):
             )[partner.id]
             self.assertEqual(rendered, expected)
 
+    @users('employee')
+    def test_render_field_no_records(self):
+        """ Test rendering on void IDs, or a list with dummy / falsy ID """
+        template = self.test_template.with_env(self.env)
+        partner = self.render_object.with_env(self.env)
+        for res_ids in ([], (), [False], [''], [None], [False, partner.id]):  # various corner cases
+            for fname, expected_obj, expected_void in zip(['subject', 'body_html'], self.base_rendered, self.base_rendered_void):
+                with self.subTest():
+                    rendered_all = template._render_field(
+                        fname,
+                        res_ids,
+                        compute_lang=True
+                    )
+                    if res_ids:
+                        self.assertTrue(res_ids[0] in rendered_all,
+                                        f'Rendering: key {repr(res_ids[0])} is considered as valid and should have an entry')
+                        self.assertEqual(rendered_all[res_ids[0]], expected_void)
+                    if len(res_ids) == 2:  # second is partner
+                        self.assertTrue(res_ids[1] in rendered_all)
+                        self.assertEqual(rendered_all[res_ids[1]], expected_obj)
+                    if not res_ids:
+                        self.assertFalse(rendered_all,
+                                         'Rendering: void input -> void output')
+
+    @users('employee')
+    def test_render_field_not_existing(self):
+        """ Test trying to render a not-existing field: raise a proper ValueError
+        instead of crashing / raising a KeyError """
+        template = self.env['mail.template'].browse(self.test_template.ids)
+        partner = self.env['res.partner'].browse(self.render_object_fr.ids)
+        with self.assertRaises(ValueError):
+            _rendered = template._render_field(
+                'not_existing',
+                partner.ids,
+                compute_lang=True
+            )[partner.id]
+
     @users('employee')
     def test_render_template_inline_template(self):
         partner = self.env['res.partner'].browse(self.render_object.ids)
diff --git a/addons/mail/wizard/mail_compose_message.py b/addons/mail/wizard/mail_compose_message.py
index 3469f43d754..8b69f6a0f36 100644
--- a/addons/mail/wizard/mail_compose_message.py
+++ b/addons/mail/wizard/mail_compose_message.py
@@ -89,7 +89,9 @@ class MailComposer(models.TransientModel):
 
     # content
     subject = fields.Char('Subject', compute=False)
-    body = fields.Html('Contents', render_engine='qweb', compute=False, default='', sanitize_style=True)
+    body = fields.Html(
+        'Contents', render_engine='qweb', render_options={'post_process': True},
+        compute=False, default='', sanitize_style=True)
     parent_id = fields.Many2one(
         'mail.message', 'Parent Message', ondelete='set null')
     template_id = fields.Many2one('mail.template', 'Use template', domain="[('model', '=', model)]")
@@ -658,7 +660,7 @@ class MailComposer(models.TransientModel):
 
         subjects = self._render_field('subject', res_ids)
         # We want to preserve comments in emails so as to keep mso conditionals
-        bodies = self._render_field('body', res_ids, post_process=True, options={'preserve_comments': self.composition_mode == 'mass_mail'})
+        bodies = self._render_field('body', res_ids, options={'preserve_comments': self.composition_mode == 'mass_mail'})
         emails_from = self._render_field('email_from', res_ids)
         replies_to = self._render_field('reply_to', res_ids)
         default_recipients = {}
diff --git a/addons/mass_mailing/controllers/main.py b/addons/mass_mailing/controllers/main.py
index 05401375eb1..2b3cfd32fc7 100644
--- a/addons/mass_mailing/controllers/main.py
+++ b/addons/mass_mailing/controllers/main.py
@@ -167,7 +167,13 @@ class MassMailController(http.Controller):
             if not self._valid_unsubscribe_token(mailing_id, res_id, email, str(token)) and not request.env.user.has_group('mass_mailing.group_mass_mailing_user'):
                 raise exceptions.AccessDenied()
 
-            html_markupsafe = mailing._render_field('body_html', [res_id])[res_id]
+            # do not force lang, will simply use user context
+            html_markupsafe = mailing._render_field(
+                'body_html',
+                [res_id],
+                compute_lang=False,
+                options={'post_process': False}
+            )[res_id]
             # Update generic URLs (without parameters) to final ones
             html_markupsafe = html_markupsafe.replace('/unsubscribe_from_list',
                                                       mailing._get_unsubscribe_url(email, res_id))
diff --git a/addons/mass_mailing/models/mailing.py b/addons/mass_mailing/models/mailing.py
index 4fc7b40989a..d95f295c1b3 100644
--- a/addons/mass_mailing/models/mailing.py
+++ b/addons/mass_mailing/models/mailing.py
@@ -73,6 +73,7 @@ class MassMailing(models.Model):
         'Subject', required=True, translate=False)
     preview = fields.Char(
         'Preview', translate=False,
+        render_engine='inline_template', render_options={'post_process': True},
         help='Catchy preview sentence that encourages recipients to open this email.\n'
              'In most inboxes, this is displayed next to the subject.\n'
              'Keep it empty if you prefer the first characters of your email content to appear instead.')
@@ -104,9 +105,9 @@ class MassMailing(models.Model):
         help="Date at which the mailing was or will be sent.")
     # don't translate 'body_arch', the translations are only on 'body_html'
     body_arch = fields.Html(string='Body', translate=False, sanitize=False)
-    body_html = fields.Html(string='Body converted to be sent by mail', render_engine='qweb', sanitize=False)
-
-   # used to determine if the mail body is empty
+    body_html = fields.Html(
+        string='Body converted to be sent by mail', sanitize=False,
+        render_engine='qweb', render_options={'post_process': True})
     is_body_empty = fields.Boolean(compute="_compute_is_body_empty")
     attachment_ids = fields.Many2many(
         'ir.attachment', 'mass_mailing_ir_attachments_rel',
diff --git a/addons/mass_mailing/wizard/mailing_mailing_test.py b/addons/mass_mailing/wizard/mailing_mailing_test.py
index 0006295a9ca..b00684fb8c6 100644
--- a/addons/mass_mailing/wizard/mailing_mailing_test.py
+++ b/addons/mass_mailing/wizard/mailing_mailing_test.py
@@ -37,10 +37,11 @@ class TestMassMailing(models.TransientModel):
         # Downside: Qweb syntax is only tested when there is atleast one record of the mailing's model
         if record:
             # Returns a proper error if there is a syntax error with Qweb
-            body = mailing._render_field('body_html', record.ids, post_process=True)[record.id]
-            preview = mailing._render_field('preview', record.ids, post_process=True)[record.id]
+            # do not force lang, will simply use user context
+            body = mailing._render_field('body_html', record.ids, compute_lang=False)[record.id]
+            preview = mailing._render_field('preview', record.ids, compute_lang=False)[record.id]
             full_body = mailing._prepend_preview(Markup(body), preview)
-            subject = mailing._render_field('subject', record.ids)[record.id]
+            subject = mailing._render_field('subject', record.ids, compute_lang=False)[record.id]
         else:
             full_body = mailing._prepend_preview(mailing.body_html, mailing.preview)
             subject = mailing.subject
diff --git a/addons/sale/wizard/sale_order_cancel.py b/addons/sale/wizard/sale_order_cancel.py
index ab445a81758..96f1c55633a 100644
--- a/addons/sale/wizard/sale_order_cancel.py
+++ b/addons/sale/wizard/sale_order_cancel.py
@@ -60,26 +60,23 @@ class SaleOrderCancel(models.TransientModel):
 
     @api.depends('order_id')
     def _compute_subject(self):
-        for wizard in self:
-            if wizard.template_id:
-                wizard.subject = self.sudo()._render_template(
-                    wizard.template_id.subject,
-                    'sale.order',
-                    [wizard.order_id.id],
-                    post_process=True,
-                )[wizard.order_id.id]
+        for wizard_su in self.filtered('template_id').sudo():
+            wizard_su.subject = wizard_su.template_id._render_field(
+                'subject',
+                [wizard_su.order_id.id],
+                compute_lang=True,
+                options={'post_process': True},
+            )[wizard_su.order_id.id]
 
     @api.depends('order_id')
     def _compute_body(self):
-        for wizard in self:
-            if wizard.template_id:
-                wizard.body = self.sudo()._render_template(
-                    wizard.template_id.body_html,
-                    'sale.order',
-                    [wizard.order_id.id],
-                    post_process=True,
-                    engine='qweb',
-                )[wizard.order_id.id]
+        for wizard_su in self.filtered('template_id').sudo():
+            wizard_su.body = wizard_su.template_id._render_field(
+                'body_html',
+                [wizard_su.order_id.id],
+                compute_lang=True,
+                options={'post_process': True},
+            )[wizard_su.order_id.id]
 
     def action_send_mail_and_cancel(self):
         self.ensure_one()
diff --git a/addons/survey/wizard/survey_invite.py b/addons/survey/wizard/survey_invite.py
index f0814ea8bf3..9c7e89514b6 100644
--- a/addons/survey/wizard/survey_invite.py
+++ b/addons/survey/wizard/survey_invite.py
@@ -210,7 +210,7 @@ class SurveyInvite(models.TransientModel):
     def _send_mail(self, answer):
         """ Create mail specific for recipient containing notably its access token """
         subject = self._render_field('subject', answer.ids)[answer.id]
-        body = self._render_field('body', answer.ids, post_process=True)[answer.id]
+        body = self._render_field('body', answer.ids)[answer.id]
         # post the message
         mail_values = {
             'attachment_ids': [(4, att.id) for att in self.attachment_ids],
diff --git a/addons/test_mail/models/test_mail_corner_case_models.py b/addons/test_mail/models/test_mail_corner_case_models.py
index e59aa431e40..31fd75ca27c 100644
--- a/addons/test_mail/models/test_mail_corner_case_models.py
+++ b/addons/test_mail/models/test_mail_corner_case_models.py
@@ -76,7 +76,7 @@ class MailTestLang(models.Model):
             group_options['has_button_access'] = True
             group_options['actions'] = [
                 {'url': self._notify_get_action_link('controller', controller='/test_mail/do_stuff', **local_msg_vals),
-                 'title': _('TestStuff')}
+                 'title': _('NotificationButtonTitle')}
             ]
         return groups
 
diff --git a/addons/test_mail/models/test_mail_models.py b/addons/test_mail/models/test_mail_models.py
index 8b3eec16f95..284e86956f6 100644
--- a/addons/test_mail/models/test_mail_models.py
+++ b/addons/test_mail/models/test_mail_models.py
@@ -225,7 +225,9 @@ class MailTestContainerMC(models.Model):
 
 class MailTestComposerMixin(models.Model):
     """ A simple invite-like wizard using the composer mixin, rendering on
-    itself. """
+    composer source test model. Purpose is to have a minimal composer which
+    runs on other records and check notably dynamic template support and
+    translations. """
     _description = 'Invite-like Wizard'
     _name = 'mail.test.composer.mixin'
     _inherit = ['mail.composer.mixin']
@@ -233,6 +235,25 @@ class MailTestComposerMixin(models.Model):
     name = fields.Char('Name')
     author_id = fields.Many2one('res.partner')
     description = fields.Html('Description', render_engine="qweb", render_options={"post_process": True}, sanitize=False)
+    source_ids = fields.Many2many('mail.test.composer.source', string='Invite source')
 
     def _compute_render_model(self):
-        self.render_model = self._name
+        self.render_model = 'mail.test.composer.source'
+
+
+class MailTestComposerSource(models.Model):
+    """ A simple model on which invites are sent. """
+    _description = 'Invite-like Wizard'
+    _name = 'mail.test.composer.source'
+    _inherit = ['mail.thread.blacklist']
+    _primary_email = 'email_from'
+
+    name = fields.Char('Name')
+    customer_id = fields.Many2one('res.partner', 'Main customer')
+    email_from = fields.Char(
+        'Email',
+        compute='_compute_email_from', readonly=False, store=True)
+
+    def _compute_email_from(self):
+        for source in self.filtered(lambda r: r.customer_id and not r.email_from):
+            source.email_from = source.customer_id.email_formatted
diff --git a/addons/test_mail/security/ir.model.access.csv b/addons/test_mail/security/ir.model.access.csv
index 0c6126ffb34..2fac058e400 100644
--- a/addons/test_mail/security/ir.model.access.csv
+++ b/addons/test_mail/security/ir.model.access.csv
@@ -19,6 +19,8 @@ access_mail_test_ticket_mc_portal,mail.test.ticket.mc.portal,model_mail_test_tic
 access_mail_test_ticket_mc_user,mail.test.ticket.mc.user,model_mail_test_ticket_mc,base.group_user,1,1,1,1
 access_mail_test_composer_mixin_all,mail.test.composer.mixin.all,model_mail_test_composer_mixin,,0,0,0,0
 access_mail_test_composer_mixin_user,mail.test.composer.mixin.user,model_mail_test_composer_mixin,base.group_user,1,1,1,1
+access_mail_test_composer_source_all,mail.test.composer.source.all,model_mail_test_composer_source,,1,0,0,0
+access_mail_test_composer_source_user,mail.test.composer.source.user,model_mail_test_composer_source,base.group_user,1,1,1,1
 access_mail_test_container_portal,mail.test.container_portal,model_mail_test_container,base.group_portal,1,0,0,0
 access_mail_test_container_user,mail.test.container.user,model_mail_test_container,base.group_user,1,1,1,1
 access_mail_test_container_mc_portal,mail.test.container.mc.portal,model_mail_test_container_mc,base.group_portal,1,0,0,0
diff --git a/addons/test_mail/tests/test_mail_composer_mixin.py b/addons/test_mail/tests/test_mail_composer_mixin.py
index 5b85c34ed5c..9591646b4a0 100644
--- a/addons/test_mail/tests/test_mail_composer_mixin.py
+++ b/addons/test_mail/tests/test_mail_composer_mixin.py
@@ -13,39 +13,101 @@ class TestMailComposerMixin(TestMailCommon, TestRecipients):
     def setUpClass(cls):
         super(TestMailComposerMixin, cls).setUpClass()
 
-        cls.mail_template = cls.env['mail.template'].create({
-            'subject': 'Subject for {{ object.name }}',
-            'body_html': '<p>Body for <t t-out="object.name"/></p>',
+        # ensure employee can create partners, necessary for templates
+        cls.user_employee.write({
+            'groups_id': [(4, cls.env.ref('base.group_partner_manager').id)],
         })
 
+        cls.mail_template = cls.env['mail.template'].create({
+            'body_html': '<p>EnglishBody for <t t-out="object.name"/></p>',
+            'model_id': cls.env['ir.model']._get('mail.test.composer.source').id,
+            'name': 'Test Template for mail.test.composer.source',
+            'lang': '{{ object.customer_id.lang }}',
+            'subject': 'EnglishSubject for {{ object.name }}',
+        })
+        cls.test_record = cls.env['mail.test.composer.source'].create({
+            'name': cls.partner_1.name,
+            'customer_id': cls.partner_1.id,
+        })
+
+        cls._activate_multi_lang(
+            layout_arch_db='<body><t t-out="message.body"/> English Layout for <t t-esc="model_description"/></body>',
+            lang_code='es_ES',
+            test_record=cls.test_record,
+            test_template=cls.mail_template,
+        )
+
     @users("employee")
     def test_content_sync(self):
-        record = self.env['mail.test.composer.mixin'].create({
+        """ Test updating template updates the dynamic fields accordingly. """
+        source = self.test_record.with_env(self.env)
+        composer = self.env['mail.test.composer.mixin'].create({
             'name': 'Invite',
             'template_id': self.mail_template.id,
+            'source_ids': [(4, source.id)],
         })
-        self.assertEqual(record.subject, self.mail_template.subject)
-        self.assertEqual(record.body, self.mail_template.body_html)
+        self.assertEqual(composer.body, self.mail_template.body_html)
+        self.assertEqual(composer.subject, self.mail_template.subject)
+        self.assertFalse(composer.lang, 'Fixme: lang is not propagated currently')
 
-        subject = record._render_field('subject', record.ids)[record.id]
-        self.assertEqual(subject, 'Subject for %s' % record.name)
-        body = record._render_field('body', record.ids)[record.id]
-        self.assertEqual(body, '<p>Body for %s</p>' % record.name)
+        subject = composer._render_field('subject', source.ids)[source.id]
+        self.assertEqual(subject, f'EnglishSubject for {source.name}')
+        body = composer._render_field('body', source.ids)[source.id]
+        self.assertEqual(body, f'<p>EnglishBody for {source.name}</p>')
 
     @users("employee")
-    def test_rendering(self):
-        record = self.env['mail.test.composer.mixin'].create({
-            'name': 'Invite',
-            'subject': 'Subject for {{ object.name }}',
-            'body': '<p>Content from <t t-out="user.name"/></p>',
+    def test_rendering_custom(self):
+        """ Test rendering with custom strings (not coming from template) """
+        source = self.test_record.with_env(self.env)
+        composer = self.env['mail.test.composer.mixin'].create({
             'description': '<p>Description for <t t-esc="object.name"/></p>',
+            'body': '<p>SpecificBody from <t t-out="user.name"/></p>',
+            'name': 'Invite',
+            'subject': 'SpecificSubject for {{ object.name }}',
         })
-        self.assertEqual(record.subject, 'Subject for {{ object.name }}')
-        self.assertEqual(record.body, '<p>Content from <t t-out="user.name"/></p>')
+        self.assertEqual(composer.body, '<p>SpecificBody from <t t-out="user.name"/></p>')
+        self.assertEqual(composer.subject, 'SpecificSubject for {{ object.name }}')
 
-        subject = record._render_field('subject', record.ids)[record.id]
-        self.assertEqual(subject, 'Subject for %s' % record.name)
-        body = record._render_field('body', record.ids)[record.id]
-        self.assertEqual(body, '<p>Content from %s</p>' % self.env.user.name)
-        description = record._render_field('description', record.ids)[record.id]
-        self.assertEqual(description, '<p>Description for Invite</p>')
+        subject = composer._render_field('subject', source.ids)[source.id]
+        self.assertEqual(subject, f'SpecificSubject for {source.name}')
+        body = composer._render_field('body', source.ids)[source.id]
+        self.assertEqual(body, f'<p>SpecificBody from {self.env.user.name}</p>')
+        description = composer._render_field('description', source.ids)[source.id]
+        self.assertEqual(description, f'<p>Description for {source.name}</p>')
+
+    @users("employee")
+    def test_rendering_lang(self):
+        """ Test rendering with language involved """
+        template = self.mail_template.with_env(self.env)
+        customer = self.partner_1.with_env(self.env)
+        customer.lang = 'es_ES'
+        source = self.test_record.with_env(self.env)
+        composer = self.env['mail.test.composer.mixin'].create({
+            'description': '<p>Description for <t t-esc="object.name"/></p>',
+            'lang': '{{ object.customer_id.lang }}',
+            'name': 'Invite',
+            'template_id': self.mail_template.id,
+            'source_ids': [(4, source.id)],
+        })
+        self.assertEqual(composer.body, template.body_html)
+        self.assertEqual(composer.subject, template.subject)
+        self.assertEqual(composer.lang, '{{ object.customer_id.lang }}')
+
+        # do not specifically ask for language computation
+        subject = composer._render_field('subject', source.ids, compute_lang=False)[source.id]
+        self.assertEqual(subject, f'EnglishSubject for {source.name}')
+        body = composer._render_field('body', source.ids, compute_lang=False)[source.id]
+        self.assertEqual(body, f'<p>EnglishBody for {source.name}</p>')
+        description = composer._render_field('description', source.ids)[source.id]
+        self.assertEqual(description, f'<p>Description for {source.name}</p>')
+
+        # ask for dynamic language computation
+        subject = composer._render_field('subject', source.ids, compute_lang=True)[source.id]
+        self.assertEqual(subject, f'EnglishSubject for {source.name}',
+                         'Fixme: translations are not done, as taking composer translations and not template one')
+        body = composer._render_field('body', source.ids, compute_lang=True)[source.id]
+        self.assertEqual(body, f'<p>EnglishBody for {source.name}</p>',
+                         'Fixme: translations are not done, as taking composer translations and not template one'
+        )
+        description = composer._render_field('description', source.ids)[source.id]
+        self.assertEqual(description, f'<p>Description for {source.name}</p>')
diff --git a/addons/test_mail/tests/test_mail_template.py b/addons/test_mail/tests/test_mail_template.py
index fb1bec1977e..678df090b6e 100644
--- a/addons/test_mail/tests/test_mail_template.py
+++ b/addons/test_mail/tests/test_mail_template.py
@@ -128,7 +128,7 @@ class TestMailTemplateLanguages(TestMailTemplateCommon):
         mail_id = test_template.send_mail(test_record.id, email_layout_xmlid='mail.test_layout')
         mail = self.env['mail.mail'].sudo().browse(mail_id)
         self.assertEqual(mail.body_html,
-                         '<body><p>SpanishBody for %s</p> Spanish Layout para Spanish description</body>' % self.test_record.name)
+                         '<body><p>SpanishBody for %s</p> Spanish Layout para Spanish Model Description</body>' % self.test_record.name)
         self.assertEqual(mail.subject, 'SpanishSubject for %s' % self.test_record.name)
 
     @mute_logger('odoo.addons.mail.models.mail_mail')
@@ -147,5 +147,5 @@ class TestMailTemplateLanguages(TestMailTemplateCommon):
         mail_id = test_template.send_mail(test_record.id, email_layout_xmlid='mail.test_layout')
         mail = self.env['mail.mail'].sudo().browse(mail_id)
         self.assertEqual(mail.body_html,
-                         '<body><p>SpanishBody for %s</p> Spanish Layout para Spanish description</body>' % self.test_record.name)
+                         '<body><p>SpanishBody for %s</p> Spanish Layout para Spanish Model Description</body>' % self.test_record.name)
         self.assertEqual(mail.subject, 'SpanishSubject for %s' % self.test_record.name)
diff --git a/addons/test_mail/tests/test_message_post.py b/addons/test_mail/tests/test_message_post.py
index 7341c9fd44a..b23052cc450 100644
--- a/addons/test_mail/tests/test_message_post.py
+++ b/addons/test_mail/tests/test_message_post.py
@@ -1210,7 +1210,49 @@ class TestMessagePostLang(TestMailCommon, TestRecipients):
 
     @users('employee')
     @mute_logger('odoo.addons.mail.models.mail_mail')
-    def test_composer_lang_template(self):
+    def test_composer_lang_template_comment(self):
+        test_record = self.test_records[0].with_user(self.env.user)
+        test_template = self.test_template.with_user(self.env.user)
+
+        with self.mock_mail_gateway():
+            test_record.message_post_with_template(
+                test_template.id,
+                composition_mode='comment',
+                email_layout_xmlid='mail.test_layout',
+                message_type='comment',
+                subtype_id=self.env.ref('mail.mt_comment').id,
+            )
+
+        record0_customer = self.env['res.partner'].search([('email_normalized', '=', 'test.record.1@test.customer.com')], limit=1)
+        self.assertTrue(record0_customer, 'Template usage should have created a contact based on record email')
+
+        customer_email = self._find_sent_mail_wemail(record0_customer.email_formatted)
+        self.assertTrue(customer_email)
+        body = customer_email['body']
+        # check content
+        self.assertIn(f'SpanishBody for {test_record.name}', body,
+                      'Body based on template should be translated')
+        # check subject
+        self.assertEqual(f'SpanishSubject for {test_record.name}', customer_email['subject'],
+                         'Subject based on template should be translated')
+        # check notification layout content
+        self.assertIn('Spanish Layout para', body, 'Layout content should be translated')
+        self.assertNotIn('English Layout for', body)
+        self.assertIn('Spanish Layout para Spanish Model Description', body, 'Model name should be translated')
+        # check notification layout strings
+        self.assertIn('View Lang Chatter Model', body,
+                      'Fixme: "View document" should be translated')
+        # self.assertIn('SpanishView Spanish Model Description', body,
+        #               '"View document" should be translated')
+        # self.assertNotIn(f'View {test_record._description}', body,
+        #                  '"View document" should be translated')
+        # self.assertIn('SpanishButtonTitle', body,
+        #               'Groups-based action names should be translated')
+        self.assertIn('NotificationButtonTitle', body, 'Fixme: Groups-based action names should be translated')
+
+    @users('employee')
+    @mute_logger('odoo.addons.mail.models.mail_mail')
+    def test_composer_lang_template_mass(self):
         test_records = self.test_records.with_user(self.env.user)
         test_template = self.test_template.with_user(self.env.user)
 
@@ -1231,11 +1273,15 @@ class TestMessagePostLang(TestMailCommon, TestRecipients):
             self.assertTrue(customer_email)
             body = customer_email['body']
             # check content
-            # self.assertIn('SpanishBody for %s' % record.name, body, 'Body based on template should be translated')
-            self.assertIn('EnglishBody for %s' % record.name, body, 'Fixme: this should be translated')
+            # self.assertIn(f'SpanishBody for {record.name}', body,
+            #               'Body based on template should be translated')
+            self.assertIn(f'EnglishBody for {record.name}', body,
+                          'Fixme: Body based on template should be translated')
             # check subject
-            # self.assertEqual('SpanishSubject for %s' % record.name, customer_email['subject'], 'Subject based on template should be translated')
-            self.assertEqual('EnglishSubject for %s' % record.name, customer_email['subject'], 'Fixme: this should be translated')
+            # self.assertEqual(f'SpanishSubject for {record.name}', customer_email['subject'],
+            #                  'Subject based on template should be translated')
+            self.assertEqual(f'EnglishSubject for {record.name}', customer_email['subject'],
+                             'Fixme: Subject based on template should be translated')
 
     @users('employee')
     @mute_logger('odoo.addons.mail.models.mail_mail')
@@ -1255,16 +1301,20 @@ class TestMessagePostLang(TestMailCommon, TestRecipients):
         customer_email = self._find_sent_mail_wemail(self.partner_2.email_formatted)
         self.assertTrue(customer_email)
         body = customer_email['body']
-        # check notification layout translation
-        self.assertIn('Spanish Layout para', body, 'Layout content should be translated')
-        self.assertNotIn('English Layout for', body)
-        self.assertIn('Spanish Layout para Spanish description', body, 'Model name should be translated')
-        self.assertIn('SpanishView Spanish description', body, '"View document" should be translated')
-        self.assertNotIn('View %s' % test_records[1]._description, body)
-        self.assertIn('TestSpanishStuff', body, 'Groups-based action names should be translated')
-        self.assertNotIn('TestStuff', body)
         # check content
-        self.assertIn('Hello', body, 'Body of posted message should be present')
+        self.assertIn('<p>Hello</p>', body, 'Body of posted message should be present')
+        # check notification layout content
+        self.assertIn('Spanish Layout para', body,
+                      'Layout content should be translated')
+        self.assertNotIn('English Layout for', body)
+        self.assertIn('Spanish Layout para Spanish Model Description', body,
+                      'Model name should be translated')
+        # check notification layout strings
+        self.assertIn('SpanishView Spanish Model Description', body,
+                      '"View document" should be translated')
+        self.assertNotIn(f'View {test_records[1]._description}', body)
+        self.assertIn('SpanishButtonTitle', body, 'Groups-based action names should be translated')
+        self.assertNotIn('NotificationButtonTitle', body)
 
     @users('employee')
     @mute_logger('odoo.addons.mail.models.mail_mail')
@@ -1288,15 +1338,23 @@ class TestMessagePostLang(TestMailCommon, TestRecipients):
             customer_email = self._find_sent_mail_wemail(customer.email_formatted)
             self.assertTrue(customer_email)
             body = customer_email['body']
-            # check notification layout translation
-            self.assertIn('Spanish Layout para', body, 'Layout content should be translated')
-            self.assertNotIn('English Layout for', body)
-            self.assertIn('Spanish Layout para Spanish description', body, 'Model name should be translated')
-            # self.assertIn('SpanishView Spanish description', body, '"View document" should be translated')
-            self.assertIn('View %s' % test_records[1]._description, body, 'Fixme: this should be translated')
-            # self.assertIn('TestSpanishStuff', body, 'Groups-based action names should be translated')
-            self.assertIn('TestStuff', body, 'Fixme: groups-based action names should be translated')
             # check content
-            self.assertIn('SpanishBody for %s' % record.name, body, 'Body based on template should be translated')
+            self.assertIn(f'SpanishBody for {record.name}', body,
+                          'Body based on template should be translated')
             # check subject
-            self.assertEqual('SpanishSubject for %s' % record.name, customer_email['subject'], 'Subject based on template should be translated')
+            self.assertEqual(f'SpanishSubject for {record.name}', customer_email['subject'],
+                             'Subject based on template should be translated')
+            # check notification layout translation
+            self.assertIn('Spanish Layout para', body,
+                          'Layout content should be translated')
+            self.assertNotIn('English Layout for', body)
+            self.assertIn('Spanish Layout para Spanish Model Description', body,
+                          'Model name should be translated')
+            # self.assertIn('SpanishView Spanish Model Description', body,
+            #               '"View document" should be translated')
+            self.assertIn(f'View {test_records[1]._description}', body,
+                          'Fixme: "View document" should be translated')
+            # self.assertIn('NotificationButtonTitle', body,
+            #               'Groups-based action names should be translated')
+            self.assertIn('NotificationButtonTitle', body,
+                          'Fixme: groups-based action names should be translated')
diff --git a/addons/website_slides/wizard/slide_channel_invite.py b/addons/website_slides/wizard/slide_channel_invite.py
index be8ef6490c2..d4e32cfbcd8 100644
--- a/addons/website_slides/wizard/slide_channel_invite.py
+++ b/addons/website_slides/wizard/slide_channel_invite.py
@@ -67,7 +67,7 @@ class SlideChannelInvite(models.TransientModel):
     def _prepare_mail_values(self, slide_channel_partner):
         """ Create mail specific for recipient """
         subject = self._render_field('subject', slide_channel_partner.ids)[slide_channel_partner.id]
-        body = self._render_field('body', slide_channel_partner.ids, post_process=True)[slide_channel_partner.id]
+        body = self._render_field('body', slide_channel_partner.ids)[slide_channel_partner.id]
         # post the message
         mail_values = {
             'email_from': self.env.user.email_formatted,