diff --git a/addons/im_livechat/models/mail_channel.py b/addons/im_livechat/models/mail_channel.py
index 05b8174783d..8f7b9e6dd40 100644
--- a/addons/im_livechat/models/mail_channel.py
+++ b/addons/im_livechat/models/mail_channel.py
@@ -71,19 +71,6 @@ class MailChannel(models.Model):
                 channel_infos_dict[channel.id]['livechat_visitor'] = channel._channel_get_livechat_visitor_info()
         return list(channel_infos_dict.values())
 
-    @api.model
-    def channel_fetch_slot(self):
-        values = super(MailChannel, self).channel_fetch_slot()
-        livechat_channels = self.env['mail.channel'].search([
-            ('channel_type', '=', 'livechat'),
-            ('channel_last_seen_partner_ids', 'in', self.env['mail.channel.partner'].sudo()._search([
-                ('partner_id', '=', self.env.user.partner_id.id),
-                ('is_pinned', '=', True)])
-            ),
-        ])
-        values['channel_livechat'] = livechat_channels.channel_info()
-        return values
-
     def _channel_get_livechat_visitor_info(self):
         self.ensure_one()
         # remove active test to ensure public partner is taken into account
diff --git a/addons/im_livechat/models/res_partner.py b/addons/im_livechat/models/res_partner.py
index 4359b77206f..ffc86a5b89d 100644
--- a/addons/im_livechat/models/res_partner.py
+++ b/addons/im_livechat/models/res_partner.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import models, api
+from odoo import models
 
 
 class Partners(models.Model):
@@ -33,3 +33,15 @@ class Partners(models.Model):
         else:
             result = super(Partners, self).name_get()
         return result
+
+    def _get_channels_as_member(self):
+        values = super()._get_channels_as_member()
+        livechat_channels = self.env['mail.channel'].search([
+            ('channel_type', '=', 'livechat'),
+            ('channel_last_seen_partner_ids', 'in', self.env['mail.channel.partner'].sudo()._search([
+                ('partner_id', '=', self.id),
+                ('is_pinned', '=', True),
+            ])),
+        ])
+        values['channel_livechat'] = livechat_channels.channel_info()
+        return values
diff --git a/addons/im_livechat/static/tests/helpers/mock_server.js b/addons/im_livechat/static/tests/helpers/mock_server.js
index f0c84c544e6..c67bff03f17 100644
--- a/addons/im_livechat/static/tests/helpers/mock_server.js
+++ b/addons/im_livechat/static/tests/helpers/mock_server.js
@@ -79,23 +79,6 @@ MockServer.include({
         const mailChannel = this._getRecords('mail.channel', [['uuid', '=', uuid]])[0];
         this._mockMailChannelNotifyTyping([mailChannel.id], is_typing, context);
     },
-    /**
-     * @override
-     */
-    _mockRouteMailInitMessaging() {
-        const initMessaging = this._super(...arguments);
-
-        const livechats = this._getRecords('mail.channel', [
-            ['channel_type', '=', 'livechat'],
-            ['is_pinned', '=', true],
-            ['members', 'in', this.currentPartnerId],
-        ]);
-        initMessaging.channel_slots.channel_livechat = this._mockMailChannelChannelInfo(
-            livechats.map(channel => channel.id)
-        );
-
-        return initMessaging;
-    },
 
     //--------------------------------------------------------------------------
     // Private Mocked Methods
@@ -256,4 +239,19 @@ MockServer.include({
         this._mockMailChannel_broadcast([mailChannelId], [operator.partner_id]);
         return this._mockMailChannelChannelInfo([mailChannelId])[0];
     },
+    /**
+     * @override
+     */
+    _mockResPartner_GetChannelsAsMember(ids) {
+        const partner = this._getRecords('res.partner', [['id', 'in', ids]])[0];
+        const livechats = this._getRecords('mail.channel', [
+            ['channel_type', '=', 'livechat'],
+            ['is_pinned', '=', true],
+            ['members', 'in', partner.id],
+        ]);
+        return {
+            channel_livechat: this._mockMailChannelChannelInfo(livechats.map(channel => channel.id)),
+            ...this._super(ids),
+        };
+    },
 });
diff --git a/addons/im_livechat/tests/test_get_mail_channel.py b/addons/im_livechat/tests/test_get_mail_channel.py
index 969d10bd528..e7bed715a15 100644
--- a/addons/im_livechat/tests/test_get_mail_channel.py
+++ b/addons/im_livechat/tests/test_get_mail_channel.py
@@ -99,5 +99,4 @@ class TestGetMailChannel(TransactionCase):
         self.assertFalse(operator_channel_partner.is_pinned, "channel should not be pinned for operator initially")
         self.env['mail.channel'].browse(channel_info['id']).message_post(body='cc')
         self.assertTrue(operator_channel_partner.is_pinned, "channel should be pinned for operator after visitor sent a message")
-        init_channels = self.env['mail.channel'].with_user(operator_channel_partner.partner_id.user_ids[0]).channel_fetch_slot()
-        self.assertIn(channel_info['id'], [init_channel_info['id'] for init_channel_info in init_channels['channel_livechat']], "channel should be fetched by operator on new page")
+        self.assertIn(channel_info['id'], [init_channel_info['id'] for init_channel_info in operator_channel_partner.partner_id._get_channels_as_member()['channel_livechat']], "channel should be fetched by operator on new page")
diff --git a/addons/mail/controllers/main.py b/addons/mail/controllers/main.py
index 2904dd641b8..9934390a005 100644
--- a/addons/mail/controllers/main.py
+++ b/addons/mail/controllers/main.py
@@ -250,23 +250,11 @@ class MailController(http.Controller):
 
     @http.route('/mail/needaction', type='json', auth='user')
     def needaction(self):
-        return request.env['res.partner'].get_needaction_count()
+        return request.env.user.partner_id._get_needaction_count()
 
     @http.route('/mail/init_messaging', type='json', auth='user')
     def mail_init_messaging(self):
-        values = {
-            'needaction_inbox_counter': request.env['res.partner'].get_needaction_count(),
-            'starred_counter': request.env['res.partner'].get_starred_count(),
-            'channel_slots': request.env['mail.channel'].channel_fetch_slot(),
-            'mail_failures': request.env['mail.message'].message_fetch_failed(),
-            'shortcodes': request.env['mail.shortcode'].sudo().search_read([], ['source', 'substitution', 'description']),
-            'menu_id': request.env['ir.model.data']._xmlid_to_res_id('mail.menu_root_discuss'),
-            'partner_root': request.env.ref('base.partner_root').sudo().mail_partner_format(),
-            'public_partners': [partner.mail_partner_format() for partner in request.env.ref('base.group_public').sudo().with_context(active_test=False).users.partner_id],
-            'current_partner': request.env.user.partner_id.mail_partner_format(),
-            'current_user_id': request.env.user.id,
-        }
-        return values
+        return request.env.user._init_messaging()
 
     @http.route('/mail/get_partner_info', type='json', auth='user')
     def message_partner_info_from_emails(self, model, res_ids, emails, link_mail=False):
diff --git a/addons/mail/models/mail_channel.py b/addons/mail/models/mail_channel.py
index 3a1b101fd47..721e9f4604c 100644
--- a/addons/mail/models/mail_channel.py
+++ b/addons/mail/models/mail_channel.py
@@ -822,27 +822,6 @@ class Channel(models.Model):
     # IM VIEW SPECIFIC (Slack Client Action)
     # ------------------------------------------------------------
 
-    @api.model
-    def channel_fetch_slot(self):
-        """ Return the channels of the user grouped by 'slot' (channel, direct_message or private_group), and
-            the mapping between partner_id/channel_id for direct_message channels.
-            :returns dict : the grouped channels and the mapping
-        """
-        values = {}
-        my_partner_id = self.env.user.partner_id.id
-        pinned_channels = self.env['mail.channel.partner'].search([('partner_id', '=', my_partner_id), ('is_pinned', '=', True)]).mapped('channel_id')
-
-        # get the group/public channels
-        values['channel_channel'] = self.search([('channel_type', '=', 'channel'), ('public', 'in', ['public', 'groups']), ('channel_partner_ids', 'in', [my_partner_id])]).channel_info()
-
-        # get the pinned 'direct message' channel
-        direct_message_channels = self.search([('channel_type', '=', 'chat'), ('id', 'in', pinned_channels.ids)])
-        values['channel_direct_message'] = direct_message_channels.channel_info()
-
-        # get the private group
-        values['channel_private_group'] = self.search([('channel_type', '=', 'channel'), ('public', '=', 'private'), ('channel_partner_ids', 'in', [my_partner_id])]).channel_info()
-        return values
-
     @api.model
     def channel_search_to_join(self, name=None, domain=None):
         """ Return the channel info of the channel the current partner can join
diff --git a/addons/mail/models/mail_message.py b/addons/mail/models/mail_message.py
index e6c9f36da93..88da42103d9 100644
--- a/addons/mail/models/mail_message.py
+++ b/addons/mail/models/mail_message.py
@@ -6,12 +6,10 @@ import re
 from collections import defaultdict
 
 from binascii import Error as binascii_error
-from operator import itemgetter
 
 from odoo import _, api, Command, fields, models, modules, tools
-from odoo.exceptions import AccessError, UserError
+from odoo.exceptions import AccessError
 from odoo.osv import expression
-from odoo.tools import groupby
 from odoo.tools.misc import clean_context
 
 _logger = logging.getLogger(__name__)
@@ -682,7 +680,7 @@ class Message(models.Model):
 
         ids = [n['mail_message_id'] for n in notifications.read(['mail_message_id'])]
 
-        notification = {'type': 'mark_as_read', 'message_ids': [id[0] for id in ids], 'needaction_inbox_counter': self.env.user.partner_id.get_needaction_count()}
+        notification = {'type': 'mark_as_read', 'message_ids': [id[0] for id in ids], 'needaction_inbox_counter': self.env.user.partner_id._get_needaction_count()}
         self.env['bus.bus'].sendone((self._cr.dbname, 'res.partner', partner_id), notification)
 
         return ids
@@ -706,7 +704,7 @@ class Message(models.Model):
             (self._cr.dbname, 'res.partner', partner_id.id),
             {'type': 'mark_as_read',
              'message_ids': notifications.mapped('mail_message_id').ids,
-             'needaction_inbox_counter': self.env.user.partner_id.get_needaction_count()
+             'needaction_inbox_counter': self.env.user.partner_id._get_needaction_count(),
             }
         )
 
@@ -800,18 +798,6 @@ class Message(models.Model):
 
         return vals_list
 
-    def message_fetch_failed(self):
-        """Returns all messages, sent by the current user, that have errors, in
-        the format expected by the web client."""
-        messages = self.search([
-            ('has_error', '=', True),
-            ('author_id', '=', self.env.user.partner_id.id),
-            ('res_id', '!=', 0),
-            ('model', '!=', False),
-            ('message_type', '!=', 'user_notification')
-        ])
-        return messages._message_notification_format()
-
     @api.model
     def message_fetch(self, domain, limit=20):
         """ Get a limited amount of formatted messages with provided domain.
diff --git a/addons/mail/models/res_partner.py b/addons/mail/models/res_partner.py
index 23dc76897f2..86cdf50011d 100644
--- a/addons/mail/models/res_partner.py
+++ b/addons/mail/models/res_partner.py
@@ -6,7 +6,6 @@ import logging
 from odoo import _, api, fields, models, tools
 from odoo.addons.bus.models.bus_presence import AWAY_TIMER
 from odoo.addons.bus.models.bus_presence import DISCONNECTION_TIMER
-from odoo.exceptions import AccessError
 from odoo.osv import expression
 
 _logger = logging.getLogger(__name__)
@@ -87,30 +86,65 @@ class Partner(models.Model):
             res["is_internal_user"] = not main_user.share
         return res
 
-    @api.model
-    def get_needaction_count(self):
-        """ compute the number of needaction of the current user """
-        if self.env.user.partner_id:
-            self.env['mail.notification'].flush(['is_read', 'res_partner_id'])
-            self.env.cr.execute("""
-                SELECT count(*) as needaction_count
-                FROM mail_notification R
-                WHERE R.res_partner_id = %s AND (R.is_read = false OR R.is_read IS NULL)""", (self.env.user.partner_id.id,))
-            return self.env.cr.dictfetchall()[0].get('needaction_count')
-        _logger.error('Call to needaction_count without partner_id')
-        return 0
+    def _get_needaction_count(self):
+        """ compute the number of needaction of the current partner """
+        self.ensure_one()
+        self.env['mail.notification'].flush(['is_read', 'res_partner_id'])
+        self.env.cr.execute("""
+            SELECT count(*) as needaction_count
+            FROM mail_notification R
+            WHERE R.res_partner_id = %s AND (R.is_read = false OR R.is_read IS NULL)""", (self.id,))
+        return self.env.cr.dictfetchall()[0].get('needaction_count')
 
-    @api.model
-    def get_starred_count(self):
-        """ compute the number of starred of the current user """
-        if self.env.user.partner_id:
-            self.env.cr.execute("""
-                SELECT count(*) as starred_count
-                FROM mail_message_res_partner_starred_rel R
-                WHERE R.res_partner_id = %s """, (self.env.user.partner_id.id,))
-            return self.env.cr.dictfetchall()[0].get('starred_count')
-        _logger.error('Call to starred_count without partner_id')
-        return 0
+    def _get_starred_count(self):
+        """ compute the number of starred of the current partner """
+        self.ensure_one()
+        self.env.cr.execute("""
+            SELECT count(*) as starred_count
+            FROM mail_message_res_partner_starred_rel R
+            WHERE R.res_partner_id = %s """, (self.id,))
+        return self.env.cr.dictfetchall()[0].get('starred_count')
+
+    def _message_fetch_failed(self):
+        """Returns all messages, sent by the current partner, that have errors, in
+        the format expected by the web client."""
+        self.ensure_one()
+        messages = self.env['mail.message'].search([
+            ('has_error', '=', True),
+            ('author_id', '=', self.id),
+            ('res_id', '!=', 0),
+            ('model', '!=', False),
+            ('message_type', '!=', 'user_notification')
+        ])
+        return messages._message_notification_format()
+
+    def _get_channels_as_member(self):
+        """ Return the channels of the partner grouped by 'slot' (channel, direct_message or private_group), and
+            the mapping between partner_id/channel_id for direct_message channels.
+            :returns dict : the grouped channels and the mapping
+        """
+        self.ensure_one()
+        values = {}
+        pinned_channels = self.env['mail.channel.partner'].search([('partner_id', '=', self.id), ('is_pinned', '=', True)]).mapped('channel_id')
+        # get the group/public channels
+        values['channel_channel'] = self.env['mail.channel'].search([
+            ('channel_type', '=', 'channel'),
+            ('public', 'in', ['public', 'groups']),
+            ('channel_partner_ids', 'in', [self.id]),
+        ]).channel_info()
+        # get the pinned 'direct message' channel
+        direct_message_channels = self.env['mail.channel'].search([
+            ('channel_type', '=', 'chat'),
+            ('id', 'in', pinned_channels.ids),
+        ])
+        values['channel_direct_message'] = direct_message_channels.channel_info()
+        # get the private group
+        values['channel_private_group'] = self.env['mail.channel'].search([
+            ('channel_type', '=', 'channel'),
+            ('public', '=', 'private'),
+            ('channel_partner_ids', 'in', [self.id]),
+        ]).channel_info()
+        return values
 
     @api.model
     def search_for_channel_invite(self, search_term, channel_id=None, limit=30):
diff --git a/addons/mail/models/res_users.py b/addons/mail/models/res_users.py
index 7146c6ddc44..b1a0350fc3b 100644
--- a/addons/mail/models/res_users.py
+++ b/addons/mail/models/res_users.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import _, api, exceptions, fields, models, modules, Command
+from odoo import _, api, exceptions, fields, models, modules
 from odoo.addons.base.models.res_users import is_selection_groups
 
 
@@ -80,6 +80,22 @@ class Users(models.Model):
             lambda cp: cp.channel_id.public != 'public' and cp.channel_id.channel_type == 'channel'
         ).unlink()
 
+    def _init_messaging(self):
+        self.ensure_one()
+        values = {
+            'channel_slots': self.partner_id._get_channels_as_member(),
+            'current_partner': self.partner_id.mail_partner_format(),
+            'current_user_id': self.id,
+            'mail_failures': self.partner_id._message_fetch_failed(),
+            'menu_id': self.env['ir.model.data']._xmlid_to_res_id('mail.menu_root_discuss'),
+            'needaction_inbox_counter': self.partner_id._get_needaction_count(),
+            'partner_root': self.env.ref('base.partner_root').sudo().mail_partner_format(),
+            'public_partners': [partner.mail_partner_format() for partner in self.env.ref('base.group_public').sudo().with_context(active_test=False).users.partner_id],
+            'shortcodes': self.env['mail.shortcode'].sudo().search_read([], ['source', 'substitution', 'description']),
+            'starred_counter': self.partner_id._get_starred_count(),
+        }
+        return values
+
     @api.model
     def systray_get_activities(self):
         query = """SELECT m.id, count(*), act.res_model as model,
diff --git a/addons/mail/static/tests/helpers/mock_server.js b/addons/mail/static/tests/helpers/mock_server.js
index ea5bba3159a..09e774260d3 100644
--- a/addons/mail/static/tests/helpers/mock_server.js
+++ b/addons/mail/static/tests/helpers/mock_server.js
@@ -356,70 +356,7 @@ MockServer.include({
      * @returns {Object}
      */
     _mockRouteMailInitMessaging() {
-        const channels = this._getRecords('mail.channel', [
-            ['channel_type', '=', 'channel'],
-            ['members', 'in', this.currentPartnerId],
-            ['public', 'in', ['public', 'groups']],
-        ]);
-        const channelInfos = this._mockMailChannelChannelInfo(channels.map(channel => channel.id));
-
-        const directMessages = this._getRecords('mail.channel', [
-            ['channel_type', '=', 'chat'],
-            ['is_pinned', '=', true],
-            ['members', 'in', this.currentPartnerId],
-        ]);
-        const directMessageInfos = this._mockMailChannelChannelInfo(directMessages.map(channel => channel.id));
-
-        const privateGroups = this._getRecords('mail.channel', [
-            ['channel_type', '=', 'channel'],
-            ['members', 'in', this.currentPartnerId],
-            ['public', '=', 'private'],
-        ]);
-        const privateGroupInfos = this._mockMailChannelChannelInfo(privateGroups.map(channel => channel.id));
-
-        const partnerRoot = this._getRecords(
-            'res.partner',
-            [['id', '=', this.partnerRootId]],
-            { active_test: false }
-        )[0];
-        const partnerRootFormat = this._mockResPartnerMailPartnerFormat(partnerRoot.id);
-
-        const publicPartner = this._getRecords(
-            'res.partner',
-            [['id', '=', this.publicPartnerId]],
-            { active_test: false }
-        )[0];
-        const publicPartnerFormat = this._mockResPartnerMailPartnerFormat(publicPartner.id);
-
-        const currentPartner = this._getRecords('res.partner', [['id', '=', this.currentPartnerId]])[0];
-        const currentPartnerFormat = this._mockResPartnerMailPartnerFormat(currentPartner.id);
-
-        const needaction_inbox_counter = this._mockResPartnerGetNeedactionCount();
-
-        const mailFailures = this._mockMailMessageMessageFetchFailed();
-
-        const shortcodes = this._getRecords('mail.shortcode', []);
-
-        const starredCounter = this._getRecords('mail.message', [
-            ['starred_partner_ids', 'in', this.currentPartnerId],
-        ]).length;
-
-        return {
-            channel_slots: {
-                channel_channel: channelInfos,
-                channel_direct_message: directMessageInfos,
-                channel_private_group: privateGroupInfos,
-            },
-            current_partner: currentPartnerFormat,
-            current_user_id: this.currentUserId,
-            mail_failures: mailFailures,
-            menu_id: false,
-            needaction_inbox_counter,
-            partner_root: partnerRootFormat,
-            public_partners: [publicPartnerFormat],
-            shortcodes,
-            starred_counter: starredCounter,
-        };
+        return this._mockResUsers_InitMessaging([this.currentUserId]);
     },
     /**
      * Simulates the `/mail/read_followers` route.
@@ -1166,7 +1103,7 @@ MockServer.include({
                 },
             ]);
         }
-        const notificationData = { type: 'mark_as_read', message_ids: messageIds, needaction_inbox_counter: this._mockResPartnerGetNeedactionCount() };
+        const notificationData = { type: 'mark_as_read', message_ids: messageIds, needaction_inbox_counter: this._mockResPartner_GetNeedactionCount(this.currentPartnerId) };
         const notification = [[false, 'res.partner', this.currentPartnerId], notificationData];
         this._widget.call('bus_service', 'trigger', 'notification', [notification]);
         return messageIds;
@@ -1189,30 +1126,6 @@ MockServer.include({
         messages.length = Math.min(messages.length, limit);
         return this._mockMailMessageMessageFormat(messages.map(message => message.id));
     },
-    /**
-     * Simulates `message_fetch_failed` on `mail.message`.
-     *
-     * @private
-     * @returns {Object[]}
-     */
-    _mockMailMessageMessageFetchFailed() {
-        const messages = this._getRecords('mail.message', [
-            ['author_id', '=', this.currentPartnerId],
-            ['res_id', '!=', 0],
-            ['model', '!=', false],
-            ['message_type', '!=', 'user_notification'],
-        ]).filter(message => {
-            // Purpose is to simulate the following domain on mail.message:
-            // ['notification_ids.notification_status', 'in', ['bounce', 'exception']],
-            // But it's not supported by _getRecords domain to follow a relation.
-            const notifications = this._getRecords('mail.notification', [
-                ['mail_message_id', '=', message.id],
-                ['notification_status', 'in', ['bounce', 'exception']],
-            ]);
-            return notifications.length > 0;
-        });
-        return this._mockMailMessage_MessageNotificationFormat(messages.map(message => message.id));
-    },
     /**
      * Simulates `message_format` on `mail.message`.
      *
@@ -1353,7 +1266,7 @@ MockServer.include({
                     ),
                 },
             ]);
-            const data = { type: 'mark_as_read', message_ids: [message.id], needaction_inbox_counter: this._mockResPartnerGetNeedactionCount() };
+            const data = { type: 'mark_as_read', message_ids: [message.id], needaction_inbox_counter: this._mockResPartner_GetNeedactionCount(this.currentPartnerId) };
             const busNotifications = [[[false, 'res.partner', this.currentPartnerId], data]];
             this._widget.call('bus_service', 'trigger', 'notification', busNotifications);
         }
@@ -1680,6 +1593,36 @@ MockServer.include({
         ]);
         this._mockUnlink(model, [followers.map(follower => follower.id)]);
     },
+    /**
+     * Simulates `_get_channels_as_member` on `res.partner`.
+     *
+     * @private
+     * @param {integer[]} ids
+     * @returns {Object}
+     */
+    _mockResPartner_GetChannelsAsMember(ids) {
+        const partner = this._getRecords('res.partner', [['id', 'in', ids]])[0];
+        const channels = this._getRecords('mail.channel', [
+            ['channel_type', '=', 'channel'],
+            ['members', 'in', partner.id],
+            ['public', 'in', ['public', 'groups']],
+        ]);
+        const directMessages = this._getRecords('mail.channel', [
+            ['channel_type', '=', 'chat'],
+            ['is_pinned', '=', true],
+            ['members', 'in', partner.id],
+        ]);
+        const privateGroups = this._getRecords('mail.channel', [
+            ['channel_type', '=', 'channel'],
+            ['members', 'in', partner.id],
+            ['public', '=', 'private'],
+        ]);
+        return {
+            channel_channel: this._mockMailChannelChannelInfo(channels.map(channel => channel.id)),
+            channel_direct_message: this._mockMailChannelChannelInfo(directMessages.map(channel => channel.id)),
+            channel_private_group: this._mockMailChannelChannelInfo(privateGroups.map(channel => channel.id)),
+        };
+    },
     /**
      * Simulates `get_mention_suggestions` on `res.partner`.
      *
@@ -1738,13 +1681,16 @@ MockServer.include({
         return mainMatchingPartners.concat(extraMatchingPartners);
     },
     /**
-     * Simulates `get_needaction_count` on `res.partner`.
+     * Simulates `_get_needaction_count` on `res.partner`.
      *
      * @private
+     * @param {integer} id
+     * @returns {integer}
      */
-    _mockResPartnerGetNeedactionCount() {
+    _mockResPartner_GetNeedactionCount(id) {
+        const partner = this._getRecords('res.partner', [['id', '=', id]])[0];
         return this._getRecords('mail.notification', [
-            ['res_partner_id', '=', this.currentPartnerId],
+            ['res_partner_id', '=', partner.id],
             ['is_read', '=', false],
         ]).length;
     },
@@ -1815,4 +1761,52 @@ MockServer.include({
             "name": partner.name,
         };
     },
+    /**
+     * Simulates `_message_fetch_failed` on `res.partner`.
+     *
+     * @private
+     * @param {integer} id
+     * @returns {Object[]}
+     */
+    _mockResPartner_MessageFetchFailed(id) {
+        const partner = this._getRecords('res.partner', [['id', '=', id]])[0];
+        const messages = this._getRecords('mail.message', [
+            ['author_id', '=', partner.id],
+            ['res_id', '!=', 0],
+            ['model', '!=', false],
+            ['message_type', '!=', 'user_notification'],
+        ]).filter(message => {
+            // Purpose is to simulate the following domain on mail.message:
+            // ['notification_ids.notification_status', 'in', ['bounce', 'exception']],
+            // But it's not supported by _getRecords domain to follow a relation.
+            const notifications = this._getRecords('mail.notification', [
+                ['mail_message_id', '=', message.id],
+                ['notification_status', 'in', ['bounce', 'exception']],
+            ]);
+            return notifications.length > 0;
+        });
+        return this._mockMailMessage_MessageNotificationFormat(messages.map(message => message.id));
+    },
+    /**
+     * Simulates `_init_messaging` on `res.users`.
+     *
+     * @private
+     * @param {integer[]} ids
+     * @returns {Object}
+     */
+    _mockResUsers_InitMessaging(ids) {
+        const user = this._getRecords('res.users', [['id', 'in', ids]])[0];
+        return {
+            channel_slots: this._mockResPartner_GetChannelsAsMember(user.partner_id),
+            current_partner: this._mockResPartnerMailPartnerFormat(user.partner_id),
+            current_user_id: this.currentUserId,
+            mail_failures: this._mockResPartner_MessageFetchFailed(user.partner_id),
+            menu_id: false, // not useful in QUnit tests
+            needaction_inbox_counter: this._mockResPartner_GetNeedactionCount(user.partner_id),
+            partner_root: this._mockResPartnerMailPartnerFormat(this.partnerRootId),
+            public_partners: [this._mockResPartnerMailPartnerFormat(this.publicPartnerId)],
+            shortcodes: this._getRecords('mail.shortcode', []),
+            starred_counter: this._getRecords('mail.message', [['starred_partner_ids', 'in', user.partner_id]]).length,
+        };
+    },
 });
diff --git a/addons/test_mail/tests/test_mail_thread_internals.py b/addons/test_mail/tests/test_mail_thread_internals.py
index 90545d5c2de..a8294921a76 100644
--- a/addons/test_mail/tests/test_mail_thread_internals.py
+++ b/addons/test_mail/tests/test_mail_thread_internals.py
@@ -141,7 +141,7 @@ class TestDiscuss(TestMailCommon, TestRecipients):
                          'needaction_inbox_counter': 0}
                     ]):
                 employee_partner.env['mail.message'].mark_all_as_read(domain=[])
-            na_count = employee_partner.get_needaction_count()
+            na_count = employee_partner._get_needaction_count()
             self.assertEqual(na_count, 0, "mark all as read should conclude all needactions")
 
             # mark all as read also clear inaccessible needactions
@@ -154,7 +154,7 @@ class TestDiscuss(TestMailCommon, TestRecipients):
             needaction_length = len(employee_partner.env['mail.message'].search([['needaction', '=', True]]))
             self.assertEqual(needaction_length, 1, "message should still be readable when notified")
 
-            na_count = employee_partner.get_needaction_count()
+            na_count = employee_partner._get_needaction_count()
             self.assertEqual(na_count, 1, "message not accessible is currently still counted")
 
             self._reset_bus()
@@ -166,7 +166,7 @@ class TestDiscuss(TestMailCommon, TestRecipients):
                          'needaction_inbox_counter': 0}
                     ]):
                 employee_partner.env['mail.message'].mark_all_as_read(domain=[])
-            na_count = employee_partner.get_needaction_count()
+            na_count = employee_partner._get_needaction_count()
             self.assertEqual(na_count, 0, "mark all read should conclude all needactions even inacessible ones")
 
     def test_set_message_done_user(self):