diff --git a/addons/mail/static/src/js/models/messages/message.js b/addons/mail/static/src/js/models/messages/message.js
index c733b74f347..1176c0f8c48 100644
--- a/addons/mail/static/src/js/models/messages/message.js
+++ b/addons/mail/static/src/js/models/messages/message.js
@@ -262,6 +262,7 @@ var Message =  AbstractMessage.extend(Mixins.EventDispatcherMixin, ServicesMixin
             documentID: this.getDocumentID(),
             id: id,
             imageSRC: this._getModuleIcon() || this.getAvatarSource(),
+            messageID: this.getID(),
             status: this.status,
             title: title,
         };
diff --git a/addons/mail/static/src/js/models/threads/mailbox.js b/addons/mail/static/src/js/models/threads/mailbox.js
index 28dbc4b7163..8d49d84d777 100644
--- a/addons/mail/static/src/js/models/threads/mailbox.js
+++ b/addons/mail/static/src/js/models/threads/mailbox.js
@@ -45,28 +45,6 @@ var Mailbox = SearchableThread.extend({
         num = _.isNumber(num) ? num : 1;
         this._mailboxCounter = Math.max(this._mailboxCounter - num, 0);
     },
-    /**
-     * Override so that there are options to filter messages based on document
-     * model and ID.
-     *
-     * @override
-     * @param {Object} [options]
-     * @param {string} [options.documentModel] model of the document that the
-     *   local messages of inbox must be linked to.
-     * @param {integer} [options.documentID] ID of the document that the local
-     *   messages of inbox must be linked to.
-     * @returns {mail.model.Message[]}
-     */
-    getMessages: function (options) {
-        var messages = this._super.apply(this, arguments);
-        if (options.documentModel && options.documentID) {
-            return _.filter(messages, function (message) {
-                return message.getDocumentModel() === options.documentModel &&
-                        message.getDocumentID() === options.documentID;
-            });
-        }
-        return messages;
-    },
     /**
      * Get the mailbox counter of this mailbox.
      *
@@ -89,31 +67,40 @@ var Mailbox = SearchableThread.extend({
         return this.fetchMessages().then(function (messages) {
             // pick only last message of chatter
             // items = list of objects
-            // { unreadCounter: integer, message: mail.model.Message }
+            // {
+            //    unreadCounter: {integer},
+            //    message: {mail.model.Message},
+            //    messageIDs: {integer[]},
+            // }
             var items = [];
             _.each(messages, function (message) {
                 var unreadCounter = 1;
+                var messageIDs = [message.getID()];
                 var similarItem = _.find(items, function (item) {
                     return self._areMessagesFromSameDocumentThread(item.message, message) ||
                             self._areMessagesFromSameChannel(item.message, message);
                 });
                 if (similarItem) {
                     unreadCounter = similarItem.unreadCounter + 1;
+                    messageIDs = similarItem.messagesIDs.concat(messageIDs);
                     var index = _.findIndex(items, similarItem);
                     items[index] = {
                         unreadCounter: unreadCounter,
                         message: message,
+                        messageIDs: messageIDs
                     };
                 } else {
                     items.push({
                         unreadCounter: unreadCounter,
                         message: message,
+                        messageIDs: messageIDs,
                     });
                 }
             });
             return _.map(items, function (item) {
                 return _.extend(item.message.getPreview(), {
                     unreadCounter: item.unreadCounter,
+                    messageIDs: item.messageIDs,
                 });
             });
         });
diff --git a/addons/mail/static/src/js/systray/systray_messaging_menu.js b/addons/mail/static/src/js/systray/systray_messaging_menu.js
index 5a687131504..d86e9e3913b 100644
--- a/addons/mail/static/src/js/systray/systray_messaging_menu.js
+++ b/addons/mail/static/src/js/systray/systray_messaging_menu.js
@@ -282,7 +282,11 @@ var MessagingMenu = Widget.extend({
             // e.g. needaction message of channel
             var documentID = $target.data('document-id');
             var documentModel = $target.data('document-model');
-            this._openDocument(documentModel, documentID);
+            if (!documentModel) {
+                this._openDiscuss('mailbox_inbox');
+            } else {
+                this._openDocument(documentModel, documentID);
+            }
         } else {
             // preview of thread
             this.call('mail_service', 'openThread', previewID);
@@ -300,19 +304,11 @@ var MessagingMenu = Widget.extend({
         var thread;
         var $preview = $(ev.currentTarget).closest('.o_mail_preview');
         var previewID = $preview.data('preview-id');
-        var documentModel = $preview.data('document-model');
         if (previewID === 'mailbox_inbox') {
-            var documentID = $preview.data('document-id');
-            var inbox = this.call('mail_service', 'getMailbox', 'inbox');
-            var messages = inbox.getMessages({
-                documentModel: documentModel,
-                documentID: documentID,
-            });
-            var messageIDs = _.map(messages, function (message) {
-                return message.getID();
-            });
+            var messageIDs = [].concat($preview.data('message-ids'));
             this.call('mail_service', 'markMessagesAsRead', messageIDs);
         } else if (previewID === 'mail_failure') {
+            var documentModel = $preview.data('document-model');
             var unreadCounter = $preview.data('unread-counter');
             this.do_action('mail.mail_resend_cancel_action', {
                 additional_context: {
diff --git a/addons/mail/static/src/xml/discuss.xml b/addons/mail/static/src/xml/discuss.xml
index a09b7a6f754..9d97de471ce 100644
--- a/addons/mail/static/src/xml/discuss.xml
+++ b/addons/mail/static/src/xml/discuss.xml
@@ -267,10 +267,11 @@
         @param {string} [preview.title]
         @param {string} [preview.status]
         @param {integer} [preview.unreadCounter]
+        @param {integer[]} [preview.messageIDs]
     -->
     <t t-name="mail.Preview">
         <div t-attf-class="o_mail_preview #{preview.unreadCounter &gt; 0 ? 'o_preview_unread' : ''}"
-             t-att-data-preview-id="preview.id" t-att-data-document-id="preview.documentID" t-att-data-document-model="preview.documentModel" t-att-data-unread-counter="preview.unreadCounter">
+             t-att-data-preview-id="preview.id" t-att-data-document-id="preview.documentID" t-att-data-document-model="preview.documentModel" t-att-data-unread-counter="preview.unreadCounter" t-att-data-message-ids="preview.messageIDs">
             <div t-attf-class="o_mail_preview_image #{preview.documentModel ? 'o_mail_preview_app' : ''}">
                 <img class="o_mail_preview_image" t-att-src="preview.imageSRC" alt="Preview"/>
                 <i t-if="preview.status === 'online'" class="o_mail_user_status o_user_online fa fa-circle" title="Online" role="img" aria-label="User is online"/>
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 02c7ec86e6b..30447b714b1 100644
--- a/addons/mail/static/tests/systray/systray_messaging_menu_tests.js
+++ b/addons/mail/static/tests/systray/systray_messaging_menu_tests.js
@@ -146,8 +146,8 @@ QUnit.test('messaging menu widget: messaging menu with 1 record', function (asse
     messagingMenu.destroy();
 });
 
-QUnit.test('messaging menu widget: no crash when clicking on inbox notification not associated to a document', function (assert) {
-    assert.expect(3);
+QUnit.test('messaging menu widget: open inbox for needaction not linked to any document', function (assert) {
+    assert.expect(4);
 
     var messagingMenu = new MessagingMenu();
     testUtils.addMockEnvironment(messagingMenu, {
@@ -156,17 +156,6 @@ QUnit.test('messaging menu widget: no crash when clicking on inbox notification
         session: {
             partner_id: 1,
         },
-        intercepts: {
-            /**
-             * Simulate action 'mail.action_discuss' successfully performed.
-             *
-             * @param {OdooEvent} ev
-             * @param {function} ev.data.on_success called when success action performed
-             */
-            do_action: function (ev) {
-                ev.data.on_success();
-            },
-        },
     });
     messagingMenu.appendTo($('#qunit-fixture'));
 
@@ -195,12 +184,18 @@ QUnit.test('messaging menu widget: no crash when clicking on inbox notification
     assert.strictEqual($firstChannelPreview.data('preview-id'),
         'mailbox_inbox',
         "should be a preview from channel inbox");
-    try {
-        $firstChannelPreview.click();
-        assert.ok(true, "should not have crashed when clicking on needaction preview message");
-    } finally {
-        messagingMenu.destroy();
-    }
+
+    testUtils.intercept(messagingMenu, 'do_action', function (ev) {
+        if (ev.data.action === 'mail.action_discuss') {
+            assert.step('do_action:' + ev.data.action + ':' + ev.data.options.active_id);
+        }
+    }, true);
+    $firstChannelPreview.click();
+    assert.verifySteps(
+        ['do_action:mail.action_discuss:mailbox_inbox'],
+        "should open Discuss with Inbox");
+
+    messagingMenu.destroy();
 });
 
 QUnit.test("messaging menu widget: mark as read on thread preview", function ( assert ) {
@@ -432,5 +427,101 @@ QUnit.test('update messaging preview on receiving a new message in channel previ
     messagingMenu.destroy();
 });
 
+QUnit.test('preview of inbox message not linked to document + mark as read', function (assert) {
+    assert.expect(17);
+
+    this.data.initMessaging = {
+        needaction_inbox_counter: 2,
+    };
+
+    var needactionMessages = [{
+        author_id: [1, "Demo"],
+        body: "<p>*Message1*</p>",
+        id: 689,
+        needaction: true,
+        needaction_partner_ids: [44],
+    }, {
+        author_id: [1, "Demo"],
+        body: "<p>*Message2*</p>",
+        id: 690,
+        needaction: true,
+        needaction_partner_ids: [44],
+    }];
+    this.data['mail.message'].records =
+        this.data['mail.message'].records.concat(needactionMessages);
+
+    var messagingMenu = new MessagingMenu();
+    testUtils.addMockEnvironment(messagingMenu, {
+        services: this.services,
+        data: this.data,
+        session: {
+            partner_id: 44,
+        },
+        mockRPC: function (route, args) {
+            if (args.method === 'set_message_done') {
+                assert.step({
+                    method: 'set_message_done',
+                    messageIDs: args.args[0],
+                });
+            }
+            return this._super.apply(this, arguments);
+        },
+    });
+    messagingMenu.appendTo($('#qunit-fixture'));
+    assert.strictEqual(messagingMenu.$('.o_notification_counter').text(), '2',
+        "should display a counter of 2 on the messaging menu icon");
+
+    messagingMenu.$('.dropdown-toggle').click();
+
+    assert.strictEqual(messagingMenu.$('.o_mail_preview').length, 2,
+        "should display two previews");
+
+    var $preview1 = messagingMenu.$('.o_mail_preview').eq(0);
+    var $preview2 = messagingMenu.$('.o_mail_preview').eq(1);
+
+    assert.strictEqual($preview1.data('preview-id'),
+        "mailbox_inbox",
+        "1st preview should be from the mailbox inbox");
+    assert.strictEqual($preview2.data('preview-id'),
+        "mailbox_inbox",
+        "2nd preview should also be from the mailbox inbox");
+    assert.ok($preview1.hasClass('o_preview_unread'),
+        "1st preview should be marked as unread");
+    assert.ok($preview2.hasClass('o_preview_unread'),
+        "2nd preview should also be marked as unread");
+    assert.strictEqual($preview1.find('.o_last_message_preview').text().replace(/\s/g, ''),
+        "Demo:*Message1*", "should correctly display the 1st preview");
+    assert.strictEqual($preview2.find('.o_last_message_preview').text().replace(/\s/g, ''),
+        "Demo:*Message2*", "should correctly display the 2nd preview");
+
+    $preview1.find('.o_mail_preview_mark_as_read').click();
+    assert.verifySteps([{
+            method: 'set_message_done',
+            messageIDs: [689],
+        }], "should mark 1st preview as read");
+    assert.strictEqual(messagingMenu.$('.o_notification_counter').text(), '1',
+        "should display a counter of 1 on the messaging menu icon after marking one preview as read");
+    assert.strictEqual(messagingMenu.$('.o_mail_preview').length, 1,
+        "should display a single preview remaining");
+    assert.strictEqual(messagingMenu.$('.o_mail_preview .o_last_message_preview').text().replace(/\s/g, ''),
+        "Demo:*Message2*", "preview 2 should be the remaining one");
+
+    $preview2 = messagingMenu.$('.o_mail_preview');
+    $preview2.find('.o_mail_preview_mark_as_read').click();
+    assert.verifySteps([{
+        method: 'set_message_done',
+        messageIDs: [689],
+    }, {
+        method: 'set_message_done',
+        messageIDs: [690],
+    }], "should mark 2nd preview as read");
+    assert.strictEqual(messagingMenu.$('.o_notification_counter').text(), '0',
+        "should display a counter of 0 on the messaging menu icon after marking both previews as read");
+    assert.strictEqual(messagingMenu.$('.o_mail_preview').length, 0,
+        "should display no preview remaining");
+
+    messagingMenu.destroy();
+});
+
 });
 });