diff --git a/addons/mail/models/mail_channel.py b/addons/mail/models/mail_channel.py
index 180a995a68f..37b4d222c26 100644
--- a/addons/mail/models/mail_channel.py
+++ b/addons/mail/models/mail_channel.py
@@ -730,7 +730,11 @@ class Channel(models.Model):
         self.ensure_one()
         if self.channel_message_ids.ids:
             last_message_id = self.channel_message_ids.ids[0] # zero is the index of the last message
-            self.env['mail.channel.partner'].search([('channel_id', 'in', self.ids), ('partner_id', '=', self.env.user.partner_id.id)]).write({
+            channel_partner = self.env['mail.channel.partner'].search([('channel_id', 'in', self.ids), ('partner_id', '=', self.env.user.partner_id.id)])
+            if channel_partner.seen_message_id.id == last_message_id:
+                # last message seen by user is already up-to-date
+                return
+            channel_partner.write({
                 'seen_message_id': last_message_id,
                 'fetched_message_id': last_message_id,
             })
@@ -739,7 +743,11 @@ class Channel(models.Model):
                 'last_message_id': last_message_id,
                 'partner_id': self.env.user.partner_id.id,
             }
-            self.env['bus.bus'].sendmany([[(self._cr.dbname, 'mail.channel', self.id), data]])
+            if self.channel_type == 'chat':
+                self.env['bus.bus'].sendmany([[(self._cr.dbname, 'mail.channel', self.id), data]])
+            else:
+                data['channel_id'] = self.id
+                self.env['bus.bus'].sendone((self._cr.dbname, 'res.partner', self.env.user.partner_id.id), data)
             return last_message_id
 
     @api.multi
@@ -750,8 +758,14 @@ class Channel(models.Model):
         for channel in self:
             if not channel.channel_message_ids.ids:
                 return
+            if channel.channel_type != 'chat':
+                return
             last_message_id = channel.channel_message_ids.ids[0] # zero is the index of the last message
-            self.env['mail.channel.partner'].search([('channel_id', '=', channel.id), ('partner_id', '=', self.env.user.partner_id.id)]).write({
+            channel_partner = self.env['mail.channel.partner'].search([('channel_id', '=', channel.id), ('partner_id', '=', self.env.user.partner_id.id)])
+            if channel_partner.fetched_message_id.id == last_message_id:
+                # last message fetched by user is already up-to-date
+                return
+            channel_partner.write({
                 'fetched_message_id': last_message_id,
             })
             data = {
diff --git a/addons/mail/static/src/js/models/threads/channel.js b/addons/mail/static/src/js/models/threads/channel.js
index a2316edb7be..9f0f37264db 100644
--- a/addons/mail/static/src/js/models/threads/channel.js
+++ b/addons/mail/static/src/js/models/threads/channel.js
@@ -1,7 +1,6 @@
 odoo.define('mail.model.Channel', function (require) {
 "use strict";
 
-var ChannelSeenMixin = require('mail.model.ChannelSeenMixin');
 var SearchableThread = require('mail.model.SearchableThread');
 var ThreadTypingMixin = require('mail.model.ThreadTypingMixin');
 var mailUtils = require('mail.utils');
@@ -17,7 +16,7 @@ var time = require('web.time');
  * Any piece of code in JS that make use of channels must ideally interact with
  * such objects, instead of direct data from the server.
  */
-var Channel = SearchableThread.extend(ChannelSeenMixin, ThreadTypingMixin, {
+var Channel = SearchableThread.extend(ThreadTypingMixin, {
     /**
      * @override
      * @param {Object} params
@@ -50,7 +49,6 @@ var Channel = SearchableThread.extend(ChannelSeenMixin, ThreadTypingMixin, {
     init: function (params) {
         var self = this;
         this._super.apply(this, arguments);
-        ChannelSeenMixin.init.apply(this, arguments);
         ThreadTypingMixin.init.apply(this, arguments);
 
         var data = params.data;
@@ -405,6 +403,21 @@ var Channel = SearchableThread.extend(ChannelSeenMixin, ThreadTypingMixin, {
             kwargs: { is_typing: params.typing },
         }, { shadow: true });
     },
+    /**
+     * @private
+     * @returns {$.Promise<integer>} resolved with ID of last seen message
+     */
+    _notifySeen: function () {
+        var self = this;
+        return this._rpc({
+            model: 'mail.channel',
+            method: 'channel_seen',
+            args: [[this._id]],
+        }, { shadow: true }).then(function (lastSeenMessageID) {
+            self._lastSeenMessageID = lastSeenMessageID;
+            return lastSeenMessageID;
+        });
+    },
     /**
      * Prepare and send a message to the server on this channel.
      *
diff --git a/addons/mail/static/src/js/models/threads/dm_chat.js b/addons/mail/static/src/js/models/threads/dm_chat.js
index 5e69dbeff8c..0f9d3a32294 100644
--- a/addons/mail/static/src/js/models/threads/dm_chat.js
+++ b/addons/mail/static/src/js/models/threads/dm_chat.js
@@ -1,13 +1,14 @@
 odoo.define('mail.model.DMChat', function (require) {
 "use strict";
 
+var ChannelSeenMixin = require('mail.model.ChannelSeenMixin');
 var TwoUserChannel = require('mail.model.TwoUserChannel');
 
 /**
  * Any piece of code in JS that make use of DMs must ideally interact with
  * such objects, instead of direct data from the server.
  */
-var DMChat = TwoUserChannel.extend({
+var DMChat = TwoUserChannel.extend(ChannelSeenMixin, {
     /**
      * @override
      * @param {Object} params
@@ -21,6 +22,7 @@ var DMChat = TwoUserChannel.extend({
      */
     init: function (params) {
         this._super.apply(this, arguments);
+        ChannelSeenMixin.init.apply(this, arguments);
 
         var data = params.data;
 
diff --git a/addons/mail/static/src/js/models/threads/mixins/channel_seen_mixin.js b/addons/mail/static/src/js/models/threads/mixins/channel_seen_mixin.js
index 022994673d2..20a5bba5407 100644
--- a/addons/mail/static/src/js/models/threads/mixins/channel_seen_mixin.js
+++ b/addons/mail/static/src/js/models/threads/mixins/channel_seen_mixin.js
@@ -212,26 +212,6 @@ var ChannelSeenMixin = {
         this.call('mail_service', 'getMailBus').trigger('update_channel', this.getID());
     },
 
-    //--------------------------------------------------------------------------
-    // Private
-    //--------------------------------------------------------------------------
-
-    /**
-     * @private
-     * @returns {$.Promise<integer>} resolved with ID of last seen message
-     */
-    _notifySeen: function () {
-        var self = this;
-        return this._rpc({
-            model: 'mail.channel',
-            method: 'channel_seen',
-            args: [[this._id]],
-        }, { shadow: true }).then(function (lastSeenMessageID) {
-            self._lastSeenMessageID = lastSeenMessageID;
-            return lastSeenMessageID;
-        });
-    },
-
     //--------------------------------------------------------------------------
     // Handlers
     //--------------------------------------------------------------------------
diff --git a/addons/mail/static/src/js/services/mail_notification_manager.js b/addons/mail/static/src/js/services/mail_notification_manager.js
index b59d7b91434..4aa768e4c9d 100644
--- a/addons/mail/static/src/js/services/mail_notification_manager.js
+++ b/addons/mail/static/src/js/services/mail_notification_manager.js
@@ -80,7 +80,9 @@ MailManager.include({
         if (!channel) {
             return;
         }
-        channel.updateSeenPartnersInfo(data);
+        if (channel.hasSeenFeature()) {
+            channel.updateSeenPartnersInfo(data);
+        }
     },
     /**
      * Called when a new or updated message is received on a channel
@@ -126,7 +128,9 @@ MailManager.include({
         if (!channel) {
             return;
         }
-        channel.updateSeenPartnersInfo(data);
+        if (channel.hasSeenFeature()) {
+            channel.updateSeenPartnersInfo(data);
+        }
         if (session.partner_id !== data.partner_id) {
             return;
         }
@@ -235,6 +239,27 @@ MailManager.include({
             });
         }
     },
+    /**
+     * Called when receiving a multi_user_channel seen notification. Only
+     * the current user is notified. This must be handled as if this is a
+     * channel seen notification.
+     *
+     * Note that this is a 'res.partner' notification because only the current
+     * user is notified on channel seen. This is a consequence from disabling
+     * the seen feature on multi_user_channel, because we still need to get
+     * the last seen message ID in order to display the "New Messages" separator
+     * in Discuss.
+     *
+     * @private
+     * @param {Object} data
+     * @param {integer} data.channel_id
+     * @param {string} data.info 'channel_seen'
+     * @param {integer} data.last_message_id
+     * @param {integer} data.partner_id
+     */
+    _handlePartnerChannnelSeenNotification: function (data) {
+        this._handleChannelSeenNotification(data.channel_id, data);
+    },
     /**
      * Add or remove failure when receiving a failure update message
      *
@@ -387,6 +412,8 @@ MailManager.include({
             this._handlePartnerMailFailureNotification(data);
         } else if (data.type === 'user_connection') {
             this._handlePartnerUserConnectionNotification(data);
+        } else if (data.info === 'channel_seen') {
+            this._handlePartnerChannnelSeenNotification(data);
         } else {
             this._handlePartnerChannelNotification(data);
         }
diff --git a/addons/mail/static/tests/discuss_seen_indicator_tests.js b/addons/mail/static/tests/discuss_seen_indicator_tests.js
index 41fd6a508d6..4db61a56ed1 100644
--- a/addons/mail/static/tests/discuss_seen_indicator_tests.js
+++ b/addons/mail/static/tests/discuss_seen_indicator_tests.js
@@ -80,10 +80,11 @@ QUnit.test('2 members: 1 myself message not received initially', function (asser
     assert.expect(2);
     var done = assert.async();
 
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -106,12 +107,12 @@ QUnit.test('2 members: 1 myself message not received initially', function (asser
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [3, "Me"],
@@ -130,10 +131,10 @@ QUnit.test('2 members: 1 myself message not received initially', function (asser
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
 
         assert.isVisible(discuss.$('.o_thread_message[data-message-id=100]'));
         assert.containsNone(discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]'));
@@ -147,10 +148,11 @@ QUnit.test('2 members: 1 myself message received by everyone initially', functio
     assert.expect(4);
     var done = assert.async();
 
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -173,12 +175,12 @@ QUnit.test('2 members: 1 myself message received by everyone initially', functio
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [3, "Me"],
@@ -197,10 +199,10 @@ QUnit.test('2 members: 1 myself message received by everyone initially', functio
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
         var $seenIcon = discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]');
         assert.isVisible($seenIcon, "should display seen icon on message");
         assert.containsOnce($seenIcon, '.fa-check', "should display a single check");
@@ -219,10 +221,11 @@ QUnit.test('2 members: 1 myself message seen by everyone initially', function (a
     assert.expect(4);
     var done = assert.async();
 
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -245,12 +248,12 @@ QUnit.test('2 members: 1 myself message seen by everyone initially', function (a
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [3, "Me"],
@@ -269,10 +272,10 @@ QUnit.test('2 members: 1 myself message seen by everyone initially', function (a
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
         var $seenIcon = discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]');
         assert.isVisible($seenIcon, "should display seen icon on message");
         assert.containsN($seenIcon, '.fa-check', 2, "should display 2 checks");
@@ -292,10 +295,11 @@ QUnit.test('2 members: 1 myself message received by everyone (initially not rece
     var done = assert.async();
 
     var self = this;
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -318,12 +322,12 @@ QUnit.test('2 members: 1 myself message received by everyone (initially not rece
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [3, "Me"],
@@ -342,10 +346,10 @@ QUnit.test('2 members: 1 myself message received by everyone (initially not rece
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
 
         assert.isVisible(discuss.$('.o_thread_message[data-message-id=100]'));
         assert.containsNone(discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]'));
@@ -377,10 +381,11 @@ QUnit.test('2 members: 1 myself message seen by everyone (initially not received
     var done = assert.async();
 
     var self = this;
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -403,12 +408,12 @@ QUnit.test('2 members: 1 myself message seen by everyone (initially not received
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [3, "Me"],
@@ -427,10 +432,10 @@ QUnit.test('2 members: 1 myself message seen by everyone (initially not received
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
 
         assert.isVisible(discuss.$('.o_thread_message[data-message-id=100]'));
         assert.containsNone(discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]'));
@@ -462,10 +467,11 @@ QUnit.test('2 members: 1 other message seen by me (initially not received)', fun
     var done = assert.async();
 
     var self = this;
-    var general = {
+    var dmChat = {
         id: 1,
-        channel_type: "channel",
-        name: "general",
+        channel_type: "chat",
+        direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+        name: 'DM',
         members: [{
             id: 2,
             name: "Someone",
@@ -488,12 +494,12 @@ QUnit.test('2 members: 1 other message seen by me (initially not received)', fun
 
     this.data.initMessaging = {
         channel_slots: {
-            channel_channel: [general],
+            channel_direct_message: [dmChat],
         },
     };
     this.data['mail.channel'] = {
         fields: {},
-        records: [general],
+        records: [dmChat],
     };
     this.data['mail.message'].records = [{
         author_id: [2, "Other"],
@@ -512,10 +518,10 @@ QUnit.test('2 members: 1 other message seen by me (initially not received)', fun
         services: this.services,
         session: { partner_id: 3 },
     }).then(function (discuss) {
-        // click on general
-        var $general = discuss.$('.o_mail_discuss_sidebar')
+        // click on DM chat
+        var $dmChat = discuss.$('.o_mail_discuss_sidebar')
                         .find('.o_mail_discuss_item[data-thread-id=1]');
-        testUtils.dom.click($general);
+        testUtils.dom.click($dmChat);
 
         assert.isVisible(discuss.$('.o_thread_message[data-message-id=100]'));
         assert.containsNone(discuss.$('.o_mail_thread_message_seen_icon[data-message-id=100]'));
@@ -535,7 +541,11 @@ QUnit.test('2 members: 1 other message seen by me (initially not received)', fun
     });
 });
 
-QUnit.test('3 members: 1 myself message received by some initially', function (assert) {
+QUnit.skip('3 members: 1 myself message received by some initially', function (assert) {
+    // IMPORTANT: This test make sense if this feature is on multi user channels,
+    // which was the case in case at some point. It has been disabled for
+    // performance reasons. We are unsure if this will come back in the future,
+    // so we keep to tests in 'skip' mode in the mean time.
     assert.expect(4);
     var done = assert.async();
 
@@ -624,7 +634,12 @@ QUnit.test('3 members: 1 myself message received by some initially', function (a
     });
 });
 
-QUnit.test('several members: 1 myself message seen by everyone (initially not received)', function (assert) {
+QUnit.skip('several members: 1 myself message seen by everyone (initially not received)', function (assert) {
+    // IMPORTANT: This test make sense if this feature is on multi user channels,
+    // which was the case in case at some point. It has been disabled for
+    // performance reasons. We are unsure if this will come back in the future,
+    // so we keep to tests in 'skip' mode in the mean time.
+
     // seen icon and content should change for my messages based on other users
     // actions (received and/or seen the message)
     assert.expect(26);
@@ -826,7 +841,12 @@ QUnit.test('several members: 1 myself message seen by everyone (initially not re
     });
 });
 
-QUnit.test('several members: other message seen by everyone (initially not received)', function (assert) {
+QUnit.skip('several members: other message seen by everyone (initially not received)', function (assert) {
+    // IMPORTANT: This test make sense if this feature is on multi user channels,
+    // which was the case in case at some point. It has been disabled for
+    // performance reasons. We are unsure if this will come back in the future,
+    // so we keep to tests in 'skip' mode in the mean time.
+
     // seen icon should never be visible for message of others
     assert.expect(9);
     var done = assert.async();
@@ -989,7 +1009,11 @@ QUnit.test('several members: other message seen by everyone (initially not recei
     });
 });
 
-QUnit.test('several members: only show seen icons from last message seen by everyone', function (assert) {
+QUnit.skip('several members: only show seen icons from last message seen by everyone', function (assert) {
+    // IMPORTANT: This test make sense if this feature is on multi user channels,
+    // which was the case in case at some point. It has been disabled for
+    // performance reasons. We are unsure if this will come back in the future,
+    // so we keep to tests in 'skip' mode in the mean time.
     assert.expect(12);
     var done = assert.async();
 
diff --git a/addons/mail/static/tests/systray/systray_messaging_menu_tests.js b/addons/mail/static/tests/systray/systray_messaging_menu_tests.js
index 8f4851ada0d..18a8838be7e 100644
--- a/addons/mail/static/tests/systray/systray_messaging_menu_tests.js
+++ b/addons/mail/static/tests/systray/systray_messaging_menu_tests.js
@@ -586,10 +586,18 @@ QUnit.test('grouped preview for needaction messages linked to same document', fu
     messagingMenu.destroy();
 });
 
-QUnit.test("messaging menu widget: channel seen notification", function ( assert ) {
+QUnit.test("messaging menu widget: channel seen notification", function (assert) {
     assert.expect(4);
 
-    this.data.initMessaging.channel_slots.channel_channel[0].message_unread_counter = 1;
+    this.data.initMessaging.channel_slots = {
+        channel_direct_message: [{
+            id: 1,
+            channel_type: "chat",
+            direct_partner: [{ id: 2, name: 'Someone', im_status: '' }],
+            name: 'DM',
+            message_unread_counter: 1,
+        }],
+    };
 
     var messagingMenu = new MessagingMenu();
     testUtils.mock.addMockEnvironment(messagingMenu, {
@@ -605,7 +613,7 @@ QUnit.test("messaging menu widget: channel seen notification", function ( assert
         "should have correct messaging menu counter (1 unread message in channel)");
     assert.strictEqual(messagingMenu.$('.o_preview_counter').text().replace(/\s/g, ''),
         '(1)',
-        "should display 1 unread message on general channel preview");
+        "should display 1 unread message on DM channel preview");
 
     // Simulate received channel seen notification
     var message = {
@@ -621,7 +629,7 @@ QUnit.test("messaging menu widget: channel seen notification", function ( assert
     assert.strictEqual(messagingMenu.$('.o_notification_counter').text(), '0',
         "should no longer have a messaging menu counter (no unread message in channel)");
     assert.strictEqual(messagingMenu.$('.o_preview_counter').text().replace(/\s/g, ''), '',
-        "should no longer display unread message on general channel preview");
+        "should no longer display unread message on DM channel preview");
 
     messagingMenu.destroy();
 });