diff --git a/addons/account/data/mail_template_data.xml b/addons/account/data/mail_template_data.xml
index 81eb47ad08e..13f5c49d452 100644
--- a/addons/account/data/mail_template_data.xml
+++ b/addons/account/data/mail_template_data.xml
@@ -54,8 +54,7 @@
     </p>
 </div>
             </field>
-            <field name="report_template" ref="account_invoices"/>
-            <field name="report_name">Invoice_{{ (object.name or '').replace('/','_') }}{{ object.state == 'draft' and '_draft' or '' }}</field>
+            <field name="report_template_ids" eval="[(4, ref('account.account_invoices'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -84,8 +83,7 @@
     </p>
 </div>
 </field>
-            <field name="report_template" ref="account.action_report_payment_receipt"/>
-            <field name="report_name">{{ (object.name or '').replace('/','-') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('account.action_report_payment_receipt'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -129,8 +127,7 @@
     </p>
 </div>
             </field>
-            <field name="report_template" ref="account_invoices"/>
-            <field name="report_name">Credit_note_{{ (object.name or '').replace('/','_') }}{{ object.state == 'draft' and '_draft' or '' }}</field>
+            <field name="report_template_ids" eval="[(4, ref('account.account_invoices'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
diff --git a/addons/event/data/mail_template_data.xml b/addons/event/data/mail_template_data.xml
index 1d5de71bdec..03d541a588d 100644
--- a/addons/event/data/mail_template_data.xml
+++ b/addons/event/data/mail_template_data.xml
@@ -22,8 +22,7 @@
         <t t-out="object.event_id.user_id.signature or ''">--<br/>Mitchell Admin</t>
     </t>
 </div></field>
-            <field name="report_template" ref="action_report_event_registration_foldable_badge"/>
-            <field name="report_name">Foldable Badge - {{ (object.event_id.name or 'Event').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('event.action_report_event_registration_foldable_badge'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -254,8 +253,7 @@
 </td></tr>
 </table>
             </field>
-            <field name="report_template" ref="action_report_event_registration_full_page_ticket"/>
-            <field name="report_name">Full Page Ticket - {{ (object.event_id.name or 'Event').replace('/','') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('event.action_report_event_registration_full_page_ticket'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
         </record>
 
diff --git a/addons/loyalty/data/mail_template_data.xml b/addons/loyalty/data/mail_template_data.xml
index 4c4a8597811..bba70470e01 100644
--- a/addons/loyalty/data/mail_template_data.xml
+++ b/addons/loyalty/data/mail_template_data.xml
@@ -34,8 +34,7 @@
                 </div>
             </div>
         </field>
-        <field name="report_template" ref="loyalty.report_gift_card"/>
-        <field name="report_name">Your Gift Card</field>
+        <field name="report_template_ids" eval="[(4, ref('loyalty.report_gift_card'))]"/>
         <field name="auto_delete" eval="True"/>
     </record>
 
@@ -96,8 +95,7 @@
 </tr>
 </tbody></table>
         </field>
-        <field name="report_template" ref="loyalty.report_loyalty_card"/>
-        <field name="report_name">Your Coupon Code</field>
+        <field name="report_template_ids" eval="[(4, ref('loyalty.report_loyalty_card'))]"/>
         <field name="auto_delete" eval="True"/>
     </record>
 </odoo>
diff --git a/addons/mail/models/mail_template.py b/addons/mail/models/mail_template.py
index 25c734bbac0..bccd11d813c 100644
--- a/addons/mail/models/mail_template.py
+++ b/addons/mail/models/mail_template.py
@@ -7,6 +7,7 @@ import logging
 from odoo import _, api, fields, models, tools, Command
 from odoo.exceptions import UserError
 from odoo.tools import is_html_empty
+from odoo.tools.safe_eval import safe_eval, time
 
 _logger = logging.getLogger(__name__)
 
@@ -63,10 +64,12 @@ class MailTemplate(models.Model):
                                       'attachment_id', 'Attachments',
                                       help="You may attach files to this template, to be added to all "
                                            "emails created from this template")
-    report_name = fields.Char('Report Filename', translate=True, prefetch=True,
-                              help="Name to use for the generated report file (may contain placeholders)\n"
-                                   "The extension can be omitted and will then come from the report type.")
-    report_template = fields.Many2one('ir.actions.report', 'Optional report to print and attach')
+    report_template_ids = fields.Many2many(
+        'ir.actions.report', relation='mail_template_ir_actions_report_rel',
+        column1='mail_template_id',
+        column2='ir_actions_report_id',
+        string='Reports to print and attach',
+        domain="[('model', '=', model)]")
     # options
     mail_server_id = fields.Many2one('ir.mail_server', 'Outgoing Mail Server', readonly=False,
                                      help="Optional preferred server for outgoing mails. If not set, the highest "
@@ -198,14 +201,14 @@ class MailTemplate(models.Model):
     def _generate_template_attachments(self, res_ids, render_fields,
                                        render_results=None):
         """ Render attachments of template 'self', returning values for records
-        given by 'res_ids'. Note that ``report_template`` returns values for
+        given by 'res_ids'. Note that ``report_template_ids`` returns values for
         'attachments', as we have a list of tuple (report_name, base64 value)
         for those reports. It is considered as being the job of callers to
         transform those attachments into valid ``ir.attachment`` records.
 
         :param list res_ids: list of record IDs on which template is rendered;
         :param list render_fields: list of fields to render on template which
-          are specific to attachments, e.g. attachment_ids or report_template;
+          are specific to attachments, e.g. attachment_ids or report_template_ids;
         :param dict render_results: res_ids-based dictionary of render values.
           For each res_id, a dict of values based on render_fields is given
 
@@ -215,6 +218,11 @@ class MailTemplate(models.Model):
         if render_results is None:
             render_results = {}
 
+        # generating reports is done on a per-record basis, better ensure cache
+        # is filled up to avoid rendering and browsing in a loop
+        if res_ids and 'report_template_ids' in render_fields and self.report_template_ids:
+            self.env[self.model].browse(res_ids)
+
         for res_id in res_ids:
             values = render_results.setdefault(res_id, {})
 
@@ -223,27 +231,33 @@ class MailTemplate(models.Model):
                 values['attachment_ids'] = self.attachment_ids.ids
 
             # generate attachments (reports)
-            if 'report_template' in render_fields and self.report_template:
-                report = self.report_template
-
-                if report.report_type in ['qweb-html', 'qweb-pdf']:
-                    report_content, report_format = self.env['ir.actions.report']._render_qweb_pdf(report, [res_id])
-                else:
-                    render_res = self.env['ir.actions.report']._render(report, [res_id])
-                    if not render_res:
-                        raise UserError(_('Unsupported report type %s found.', report.report_type))
-                    report_content, report_format = render_res
-                report_content = base64.b64encode(report_content)
-
-                report_name = self._render_field('report_name', [res_id])[res_id]
-                if not report_name:
-                    report_name = 'report.' + report.report_name
-                ext = "." + report_format
-                if not report_name.endswith(ext):
-                    report_name += ext
-
-                values['attachments'] = [(report_name, report_content)]
-            elif 'report_template' in render_fields:
+            if 'report_template_ids' in render_fields and self.report_template_ids:
+                for report in self.report_template_ids:
+                    # generate content
+                    if report.report_type in ['qweb-html', 'qweb-pdf']:
+                        report_content, report_format = self.env['ir.actions.report']._render_qweb_pdf(report, [res_id])
+                    else:
+                        render_res = self.env['ir.actions.report']._render(report, [res_id])
+                        if not render_res:
+                            raise UserError(_('Unsupported report type %s found.', report.report_type))
+                        report_content, report_format = render_res
+                    report_content = base64.b64encode(report_content)
+                    # generate name
+                    if report.print_report_name:
+                        report_name = safe_eval(
+                            report.print_report_name,
+                            {
+                                'object': self.env[self.model].browse(res_id),
+                                'time': time,
+                            }
+                        )
+                    else:
+                        report_name = _('Report')
+                    extension = "." + report_format
+                    if not report_name.endswith(extension):
+                        report_name += extension
+                    values.setdefault('attachments', []).append((report_name, report_content))
+            elif 'report_template_ids' in render_fields:
                 values['attachments'] = []
 
         # hook for attachments-specific computation, used currently only for accounting
@@ -436,7 +450,7 @@ class MailTemplate(models.Model):
             'email_cc',  # recipients
             'email_to',  # recipients
             'partner_to',  # recipients
-            'report_template',  # attachments
+            'report_template_ids',  # attachments
             'scheduled_date',  # specific
             # not rendered (static)
             'auto_delete',
@@ -482,7 +496,7 @@ class MailTemplate(models.Model):
             )
 
             # generate attachments if requested
-            if render_fields_set & {'attachment_ids', 'report_template'}:
+            if render_fields_set & {'attachment_ids', 'report_template_ids'}:
                 template._generate_template_attachments(
                     template_res_ids,
                     render_fields_set,
@@ -533,7 +547,7 @@ class MailTemplate(models.Model):
              'model',
              'partner_to',
              'reply_to',
-             'report_template',
+             'report_template_ids',
              'res_id',
              'scheduled_date',
              'subject',
diff --git a/addons/mail/views/mail_template_views.xml b/addons/mail/views/mail_template_views.xml
index 021e0dde091..0be8580fb0d 100644
--- a/addons/mail/views/mail_template_views.xml
+++ b/addons/mail/views/mail_template_views.xml
@@ -79,8 +79,9 @@
                                     <field name="lang" placeholder="{{ object.partner_id.lang }}"/>
                                     <field name="mail_server_id"/>
                                     <field name="auto_delete"/>
-                                    <field name="report_template" domain="[('model','=',model)]"/>
-                                    <field name="report_name" attrs="{'invisible':[('report_template','=',False)]}"/>
+                                    <field name="report_template_ids" domain="[('model','=',model)]"
+                                        widget="many2many_tags"
+                                        options="{'no_create': True}"/>
                                 </group>
                             </page>
                         </notebook>
@@ -102,7 +103,6 @@
                     <field name="email_from" optional="hidden"/>
                     <field name="email_to" optional="hidden"/>
                     <field name="partner_to" optional="hidden"/>
-                    <field name="report_name" optional="hidden"/>
                 </tree>
             </field>
         </record>
@@ -112,7 +112,7 @@
             <field name="model">mail.template</field>
             <field name="arch" type="xml">
                 <search string="Templates">
-                    <field name="name" filter_domain="['|', '|', '|',('name','ilike',self), ('report_name','ilike',self), ('subject','ilike',self), ('email_to','ilike',self)]" string="Templates"/>
+                    <field name="name" filter_domain="['|', '|', ('name','ilike',self), ('subject','ilike',self), ('email_to','ilike',self)]" string="Templates"/>
                     <field name="lang"/>
                     <field name="model_id"/>
                     <filter name="base_templates" string="Base Templates" domain="[('template_category', '=', 'base_template')]"/>
diff --git a/addons/mail/wizard/mail_compose_message.py b/addons/mail/wizard/mail_compose_message.py
index b92fdb65867..3914e6be9d2 100644
--- a/addons/mail/wizard/mail_compose_message.py
+++ b/addons/mail/wizard/mail_compose_message.py
@@ -284,7 +284,7 @@ class MailComposer(models.TransientModel):
                  'mail_server_id',
                  'partner_ids',
                  'reply_to',
-                 'report_template',
+                 'report_template_ids',
                  'scheduled_date',
                  'subject',
                 )
@@ -709,7 +709,7 @@ class MailComposer(models.TransientModel):
                  'email_cc',
                  'mail_server_id',
                  'partner_ids',
-                 'report_template',
+                 'report_template_ids',
                  'scheduled_date',
                 )
             )
@@ -906,7 +906,7 @@ class MailComposer(models.TransientModel):
 
         # some fields behave / are named differently on template model
         mapping = {
-            'attachments': 'report_template',
+            'attachments': 'report_template_ids',
             'body': 'body_html',
             'partner_ids': 'partner_to',
         }
diff --git a/addons/mail/wizard/mail_template_preview.py b/addons/mail/wizard/mail_template_preview.py
index 14367e1e250..6eb21551de0 100644
--- a/addons/mail/wizard/mail_template_preview.py
+++ b/addons/mail/wizard/mail_template_preview.py
@@ -15,7 +15,7 @@ class MailTemplatePreview(models.TransientModel):
                              'email_from',
                              'email_to',
                              'partner_to',
-                             'report_template',
+                             'report_template_ids',
                              'reply_to',
                              'scheduled_date',
                             ]
@@ -94,9 +94,9 @@ class MailTemplatePreview(models.TransientModel):
 
     def _set_mail_attributes(self, values=None):
         for field in self._MAIL_TEMPLATE_FIELDS:
-            if field in ('partner_to', 'report_template'):
+            if field in ('partner_to', 'report_template_ids'):
                 # partner_to is used to generate partner_ids, handled here below
-                # report_template generates attachments, no usage here
+                # report_template_ids generates attachments, no usage here
                 continue
             field_value = values.get(field, False) if values else self.mail_template_id[field]
             self[field] = field_value
diff --git a/addons/purchase/data/mail_template_data.xml b/addons/purchase/data/mail_template_data.xml
index 0b348044df9..3dffc957249 100644
--- a/addons/purchase/data/mail_template_data.xml
+++ b/addons/purchase/data/mail_template_data.xml
@@ -30,8 +30,7 @@
         </t>
     </p>
 </div></field>
-            <field name="report_template" ref="report_purchase_quotation"/>
-            <field name="report_name">RFQ_{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('purchase.report_purchase_quotation'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -69,8 +68,7 @@
         <br/><br/>
     </p>
 </div></field>
-            <field name="report_template" ref="action_report_purchase_order"/>
-            <field name="report_name">PO_{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('purchase.action_report_purchase_order'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -109,8 +107,7 @@
         <br/><br/>
     </p>
 </div></field>
-            <field name="report_template" ref="action_report_purchase_order"/>
-            <field name="report_name">PO_{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('purchase.action_report_purchase_order'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
diff --git a/addons/repair/data/mail_template_data.xml b/addons/repair/data/mail_template_data.xml
index c2eb4f33f4e..cb05cf86397 100644
--- a/addons/repair/data/mail_template_data.xml
+++ b/addons/repair/data/mail_template_data.xml
@@ -28,8 +28,7 @@
         </t>
     </p>
 </div></field>
-            <field name="report_template" ref="action_report_repair_order"/>
-            <field name="report_name">{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('repair.action_report_repair_order'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
diff --git a/addons/sale/data/mail_template_data.xml b/addons/sale/data/mail_template_data.xml
index 545490d9179..be542b12212 100644
--- a/addons/sale/data/mail_template_data.xml
+++ b/addons/sale/data/mail_template_data.xml
@@ -39,8 +39,7 @@
     </p>
 </div>
             </field>
-            <field name="report_template" ref="action_report_saleorder"/>
-            <field name="report_name">{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('sale.action_report_saleorder'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
@@ -234,8 +233,7 @@
     </div>
 </t>
 </div></field>
-            <field name="report_template" ref="action_report_saleorder"/>
-            <field name="report_name">{{ (object.name or '').replace('/','_') }}</field>
+            <field name="report_template_ids" eval="[(4, ref('sale.action_report_saleorder'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
diff --git a/addons/stock/data/mail_template_data.xml b/addons/stock/data/mail_template_data.xml
index 778fa6ac710..e55142b507c 100644
--- a/addons/stock/data/mail_template_data.xml
+++ b/addons/stock/data/mail_template_data.xml
@@ -40,8 +40,7 @@
     </p>
 </div>
         </field>
-        <field name="report_template" ref="stock.action_report_delivery"/>
-        <field name="report_name">{{ (object.name or '').replace('/','_') }}</field>
+        <field name="report_template_ids" eval="[(4, ref('stock.action_report_delivery'))]"/>
         <field name="lang">{{ object.partner_id.lang }}</field>
         <field name="auto_delete" eval="True"/>
     </record>
diff --git a/addons/survey/data/mail_template_data.xml b/addons/survey/data/mail_template_data.xml
index 2bc37df0917..49ed3995a48 100644
--- a/addons/survey/data/mail_template_data.xml
+++ b/addons/survey/data/mail_template_data.xml
@@ -79,8 +79,7 @@
     </table>
 </div>
             </field>
-            <field name="report_template" ref="certification_report"/>
-            <field name="report_name">Certification Document</field>
+            <field name="report_template_ids" eval="[(4, ref('survey.certification_report'))]"/>
             <field name="lang">{{ object.partner_id.lang }}</field>
             <field name="auto_delete" eval="True"/>
         </record>
diff --git a/addons/survey/tests/test_certification_flow.py b/addons/survey/tests/test_certification_flow.py
index b3fddf2d1b2..65205a5a531 100644
--- a/addons/survey/tests/test_certification_flow.py
+++ b/addons/survey/tests/test_certification_flow.py
@@ -128,7 +128,8 @@ class TestCertificationFlow(common.TestSurveyCommon, HttpCase):
         self.assertIn("User Certification for SO lines", certification_email.subject)
         self.assertIn("employee@example.com", certification_email.email_to)
         self.assertEqual(len(certification_email.attachment_ids), 1)
-        self.assertEqual(certification_email.attachment_ids[0].name, 'Certification Document.html')
+        self.assertEqual(certification_email.attachment_ids[0].name, f'Certification - {certification.title}.html',
+                         'Default certification report print_report_name is "Certification - %s" % (object.survey_id.display_name)')
 
     def test_randomized_certification(self):
         # Step: survey user creates the randomized certification
diff --git a/addons/test_event_full/tests/common.py b/addons/test_event_full/tests/common.py
index 7231d002406..3b748164c19 100644
--- a/addons/test_event_full/tests/common.py
+++ b/addons/test_event_full/tests/common.py
@@ -120,7 +120,7 @@ class TestEventFullCommon(EventCrmCase, TestSalesCommon, MockVisitor):
         # ------------------------------------------------------------
         test_registration_report = cls.env.ref('test_event_full.event_registration_report_test')
         subscription_template = cls.env.ref('event.event_subscription')
-        subscription_template.write({'report_template': test_registration_report.id})
+        subscription_template.write({'report_template_ids': [(6, 0, test_registration_report.ids)]})
         cls.test_event_type = cls.env['event.type'].create({
             'auto_confirm': True,
             'default_timezone': 'Europe/Paris',
diff --git a/addons/test_mail/data/mail_template_data.xml b/addons/test_mail/data/mail_template_data.xml
index 944a1b7a95f..f5970d9e211 100644
--- a/addons/test_mail/data/mail_template_data.xml
+++ b/addons/test_mail/data/mail_template_data.xml
@@ -33,6 +33,17 @@
         </t>
     </template>
 
+    <template id="mail_test_ticket_test_template_2">
+        <t t-call="web.html_container">
+            <t t-set="o" t-value="res_company"/>
+            <t t-call="web.external_layout">
+                <div class="page">
+                    <p>This is another sample of an external report.</p>
+                </div>
+            </t>
+        </t>
+    </template>
+
     <template id="mail_template_simple_test">
         <p>Hello <t t-out="partner.name"/>, this comes from <t t-out="object.name"/>.</p>
     </template>
diff --git a/addons/test_mail/tests/test_mail_composer.py b/addons/test_mail/tests/test_mail_composer.py
index 0f47784412c..71f40256f1a 100644
--- a/addons/test_mail/tests/test_mail_composer.py
+++ b/addons/test_mail/tests/test_mail_composer.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+import base64
+
 from ast import literal_eval
 from datetime import timedelta
 from freezegun import freeze_time
@@ -61,13 +63,21 @@ class TestMailComposer(TestMailCommon, TestRecipients):
             additional_values={'user_id': cls.user_employee_2.id},
         )
 
-        cls.test_report = cls.env['ir.actions.report'].create({
-            'name': 'Test Report on mail test ticket',
-            'model': 'mail.test.ticket',
-            'report_type': 'qweb-pdf',
-            'report_name': 'test_mail.mail_test_ticket_test_template',
-        })
-        cls.test_record_report = cls.env['ir.actions.report']._render_qweb_pdf(cls.test_report, cls.test_record.ids)
+        cls.test_report, cls.test_report_2 = cls.env['ir.actions.report'].create([
+            {
+                'name': 'Test Report on Mail Test Ticket',
+                'model': 'mail.test.ticket',
+                'print_report_name': "'TestReport for %s' % object.name",
+                'report_type': 'qweb-pdf',
+                'report_name': 'test_mail.mail_test_ticket_test_template',
+            }, {
+                'name': 'Test Report 2 on Mail Test Ticket',
+                'model': 'mail.test.ticket',
+                'print_report_name': "'TestReport2 for %s' % object.name",
+                'report_type': 'qweb-pdf',
+                'report_name': 'test_mail.mail_test_ticket_test_template_2',
+            }
+        ])
 
         cls.test_from = '"John Doe" <john@example.com>'
 
@@ -145,14 +155,13 @@ class TestComposerForm(TestMailComposer):
         attachment_data = self._generate_attachments_data(2, self.template._name, self.template.id)
         template_1 = self.template.copy({
             'attachment_ids': [(0, 0, a) for a in attachment_data],
-            'report_name': 'TestReport for {{ object.name }}.html',  # test cursor forces html
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, (self.test_report + self.test_report_2).ids)],
         })
         template_1_attachments = template_1.attachment_ids
         self.assertEqual(len(template_1_attachments), 2)
         template_2 = self.template.copy({
             'attachment_ids': False,
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, self.test_report.ids)],
         })
 
         # begins without attachments
@@ -161,12 +170,12 @@ class TestComposerForm(TestMailComposer):
         ))
         self.assertEqual(len(composer_form.attachment_ids), 0)
 
-        # change template: 2 static (attachment_ids) and 1 dynamic (report)
+        # change template: 2 static (attachment_ids) and 2 dynamic (reports)
         composer_form.template_id = template_1
-        self.assertEqual(len(composer_form.attachment_ids), 3)
+        self.assertEqual(len(composer_form.attachment_ids), 4)
         report_attachments = [att for att in composer_form.attachment_ids if att not in template_1_attachments]
-        self.assertEqual(len(report_attachments), 1)
-        tpl_attachments = composer_form.attachment_ids[:] - report_attachments[0]
+        self.assertEqual(len(report_attachments), 2)
+        tpl_attachments = composer_form.attachment_ids[:] - self.env['ir.attachment'].concat(*report_attachments)
         self.assertEqual(tpl_attachments, template_1_attachments)
 
         # change template: 0 static (attachment_ids) and 1 dynamic (report)
@@ -174,15 +183,15 @@ class TestComposerForm(TestMailComposer):
         self.assertEqual(len(composer_form.attachment_ids), 1)
         report_attachments = [att for att in composer_form.attachment_ids if att not in template_1_attachments]
         self.assertEqual(len(report_attachments), 1)
-        tpl_attachments = composer_form.attachment_ids[:] - report_attachments[0]
+        tpl_attachments = composer_form.attachment_ids[:] - self.env['ir.attachment'].concat(*report_attachments)
         self.assertFalse(tpl_attachments)
 
         # change back to template 1
         composer_form.template_id = template_1
-        self.assertEqual(len(composer_form.attachment_ids), 3)
+        self.assertEqual(len(composer_form.attachment_ids), 4)
         report_attachments = [att for att in composer_form.attachment_ids if att not in template_1_attachments]
-        self.assertEqual(len(report_attachments), 1)
-        tpl_attachments = composer_form.attachment_ids[:] - report_attachments[0]
+        self.assertEqual(len(report_attachments), 2)
+        tpl_attachments = composer_form.attachment_ids[:] - self.env['ir.attachment'].concat(*report_attachments)
         self.assertEqual(tpl_attachments, template_1_attachments)
 
         # reset template
@@ -362,16 +371,21 @@ class TestComposerInternals(TestMailComposer):
         attachment_data = self._generate_attachments_data(3, self.template._name, self.template.id)
         self.template.write({
             'attachment_ids': [(0, 0, a) for a in attachment_data],
-            'report_name': 'TestReport for {{ object.name }}.html',  # test cursor forces html
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, (self.test_report + self.test_report_2).ids)],
         })
         template_void = self.template.copy(default={
             'attachment_ids': False,
-            'report_name': False,
-            'report_template': False,
+            'report_template_ids': False,
         })
         attachs = self.env['ir.attachment'].search([('name', 'in', [a['name'] for a in attachment_data])])
         self.assertEqual(len(attachs), 3)
+        extra_attach = self.env['ir.attachment'].create({
+            'datas': base64.b64encode(b'ExtraData'),
+            'mimetype': 'text/plain',
+            'name': 'ExtraAttFileName.txt',
+            'res_model': False,
+            'res_id': False,
+        })
 
         for composition_mode, batch in (('comment', False), ('comment', True),
                                         ('mass_mail', False), ('mass_mail', True)):
@@ -391,14 +405,16 @@ class TestComposerInternals(TestMailComposer):
 
                 # values coming from template: attachment_ids + report in comment
                 if composition_mode == 'comment' and not batch:
-                    self.assertEqual(len(composer.attachment_ids), 4)
+                    self.assertEqual(len(composer.attachment_ids), 5)
                     for attach in attachs:
                         self.assertIn(attach, composer.attachment_ids)
                     generated = composer.attachment_ids - attachs
-                    self.assertEqual(len(generated), 1, 'MailComposer: should have 1 additional attachment for report')
-                    self.assertEqual(generated.name, f'TestReport for {self.test_record.name}.html')
-                    self.assertEqual(generated.res_model, 'mail.compose.message')
-                    self.assertEqual(generated.res_id, 0)
+                    self.assertEqual(len(generated), 2, 'MailComposer: should have 2 additional attachments for reports')
+                    self.assertEqual(
+                        sorted(generated.mapped('name')),
+                        sorted([f'TestReport for {self.test_record.name}.html', f'TestReport2 for {self.test_record.name}.html']))
+                    self.assertEqual(generated.mapped('res_model'), ['mail.compose.message'] * 2)
+                    self.assertEqual(generated.mapped('res_id'), [0] * 2)
                 # values coming from template: attachment_ids only (report is dynamic)
                 else:
                     self.assertEqual(
@@ -406,16 +422,25 @@ class TestComposerInternals(TestMailComposer):
                         sorted(attachs.ids)
                     )
 
+                # manual update
+                composer.write({
+                    'attachment_ids': [(4, extra_attach.id)],
+                })
+                if composition_mode == 'comment' and not batch:
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach + generated)
+                else:
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach)
+
                 # update with template with void values: values are kept
                 composer.write({'template_id': template_void.id})
                 # currently onchange necessary
                 composer._onchange_template_id_wrapper()
 
                 if composition_mode == 'comment' and not batch:
-                    self.assertEqual(composer.attachment_ids, attachs + generated,
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach + generated,
                                      'TODO: Values are kept (should be reset ?)')
                 else:
-                    self.assertEqual(composer.attachment_ids, attachs,
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach,
                                      'TODO: Values are kept (should be reset ?)')
 
                 # reset template: values are kept
@@ -424,10 +449,10 @@ class TestComposerInternals(TestMailComposer):
                 composer._onchange_template_id_wrapper()
 
                 if composition_mode == 'comment' and not batch:
-                    self.assertEqual(composer.attachment_ids, attachs + generated,
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach + generated,
                                      'TODO: Values are kept (should be reset ?)')
                 else:
-                    self.assertEqual(composer.attachment_ids, attachs,
+                    self.assertEqual(composer.attachment_ids, attachs + extra_attach,
                                      'TODO: Values are kept (should be reset ?)')
 
     @users('employee')
@@ -973,8 +998,7 @@ class TestComposerInternals(TestMailComposer):
     def test_mail_composer_rights_attachments(self):
         """ Ensure a user without write access to a template can send an email"""
         template_1 = self.template.copy({
-            'report_name': 'TestReport for {{ object.name }} (thanks TDE).html',  # test cursor forces html
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, self.test_report.ids)],
         })
         attachment_data = self._generate_attachments_data(2, self.template._name, self.template.id)
         template_1.write({
@@ -986,7 +1010,7 @@ class TestComposerInternals(TestMailComposer):
 
         template_1_attachments = template_1.attachment_ids
         self.assertEqual(len(template_1_attachments), 2)
-        template_1_attachment_name = list(template_1_attachments.mapped('name')) + ["TestReport for TestRecord (thanks TDE).html"]
+        template_1_attachment_name = list(template_1_attachments.mapped('name')) + [f"TestReport for {self.test_record.name}.html"]
 
         composer = self.env['mail.compose.message'].with_context(
             self._get_web_context(self.test_record)
@@ -1243,8 +1267,7 @@ class TestComposerResultsComment(TestMailComposer, CronMixinCase):
             'email_to': '%s, %s, %s' % (email_to_1, email_to_2, email_to_3),
             'email_cc': email_cc_1,
             'partner_to': '%s, {{ object.customer_id.id if object.customer_id else "" }}' % self.partner_admin.id,
-            'report_name': 'TestReport for {{ object.name }}',  # test cursor forces html
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, (self.test_report + self.test_report_2).ids)],
         })
         attachs = self.env['ir.attachment'].search([('name', 'in', [a['name'] for a in attachment_data])])
         self.assertEqual(len(attachs), 2)
@@ -1346,6 +1369,7 @@ class TestComposerResultsComment(TestMailComposer, CronMixinCase):
                                                 {'name': 'AttFileName_00.txt', 'raw': b'AttContent_00', 'type': 'text/plain'},
                                                 {'name': 'AttFileName_01.txt', 'raw': b'AttContent_01', 'type': 'text/plain'},
                                                 {'name': f'TestReport for {test_record.name}.html', 'type': 'text/plain'},
+                                                {'name': f'TestReport2 for {test_record.name}.html', 'type': 'text/plain'},
                                             ]
                                         },
                                         fields_values={
@@ -1363,6 +1387,7 @@ class TestComposerResultsComment(TestMailComposer, CronMixinCase):
                                                 {'name': 'AttFileName_00.txt', 'raw': b'AttContent_00', 'type': 'text/plain'},
                                                 {'name': 'AttFileName_01.txt', 'raw': b'AttContent_01', 'type': 'text/plain'},
                                                 {'name': f'TestReport for {test_record.name}.html', 'type': 'text/plain'},
+                                                {'name': f'TestReport2 for {test_record.name}.html', 'type': 'text/plain'},
                                             ]
                                         },
                                         fields_values={
@@ -1376,7 +1401,9 @@ class TestComposerResultsComment(TestMailComposer, CronMixinCase):
                     # attachments are copied on message and linked to document
                     self.assertEqual(
                         set(message.attachment_ids.mapped('name')),
-                        set(['AttFileName_00.txt', 'AttFileName_01.txt', f'TestReport for {test_record.name}.html'])
+                        set(['AttFileName_00.txt', 'AttFileName_01.txt',
+                             f'TestReport for {test_record.name}.html',
+                             f'TestReport2 for {test_record.name}.html'])
                     )
                     self.assertEqual(set(message.attachment_ids.mapped('res_model')), set([test_record._name]))
                     self.assertEqual(set(message.attachment_ids.mapped('res_id')), set(test_record.ids))
@@ -1611,8 +1638,7 @@ class TestComposerResultsMass(TestMailComposer):
             'email_to': '%s, %s, %s' % (email_to_1, email_to_2, email_to_3),
             'email_cc': email_cc_1,
             'partner_to': '%s, {{ object.customer_id.id if object.customer_id else "" }}' % self.partner_admin.id,
-            'report_name': 'TestReport for {{ object.name }}',  # test cursor forces html
-            'report_template': self.test_report.id,
+            'report_template_ids': [(6, 0, self.test_report.ids)],
         })
         attachs = self.env['ir.attachment'].search([('name', 'in', [a['name'] for a in attachment_data])])
         self.assertEqual(len(attachs), 2)
diff --git a/addons/website_slides/models/slide_channel.py b/addons/website_slides/models/slide_channel.py
index 1399299fbdb..f86f527a9b0 100644
--- a/addons/website_slides/models/slide_channel.py
+++ b/addons/website_slides/models/slide_channel.py
@@ -145,7 +145,7 @@ class ChannelUsersRelation(models.Model):
                  'model',
                  'partner_to',
                  'reply_to',
-                 'report_template',
+                 'report_template_ids',
                  'res_id',
                  'scheduled_date',
                  'subject',