diff --git a/addons/portal/controllers/mail.py b/addons/portal/controllers/mail.py
index dc83f05a3d2..22e861063d8 100644
--- a/addons/portal/controllers/mail.py
+++ b/addons/portal/controllers/mail.py
@@ -112,7 +112,7 @@ class PortalChatter(http.Controller):
                 raise Forbidden()
             # Non-employee see only messages with not internal subtype (aka, no internal logs)
             if not request.env['res.users'].has_group('base.group_user'):
-                domain = expression.AND([['&', '&', ('subtype_id', '!=', False), ('subtype_id.internal', '=', False), ('website_published', '=', True)], domain])
+                domain = expression.AND([Message._non_employee_message_domain(), domain])
             Message = request.env['mail.message'].sudo()
         return {
             'messages': Message.search(domain, limit=limit, offset=offset).portal_message_format(),
diff --git a/addons/portal/models/mail_message.py b/addons/portal/models/mail_message.py
index 4a5d1f804d9..afe97f1b8ca 100644
--- a/addons/portal/models/mail_message.py
+++ b/addons/portal/models/mail_message.py
@@ -21,3 +21,7 @@ class MailMessage(models.Model):
         message_tree = dict((m.id, m) for m in self.sudo())
         self._message_read_dict_postprocess(message_values, message_tree)
         return message_values
+
+    @api.model
+    def _non_employee_message_domain(self):
+        return ['&', ('subtype_id', '!=', False), ('subtype_id.internal', '=', False)]
diff --git a/addons/website_mail/models/mail_message.py b/addons/website_mail/models/mail_message.py
index 34609160f1d..683990e1e67 100644
--- a/addons/website_mail/models/mail_message.py
+++ b/addons/website_mail/models/mail_message.py
@@ -26,6 +26,11 @@ class MailMessage(models.Model):
     description = fields.Char(compute="_compute_description", help='Message description: either the subject, or the beginning of the body')
     website_published = fields.Boolean(string='Published', help="Visible on the website as a comment", copy=False)
 
+    @api.model
+    def _non_employee_message_domain(self):
+        domain = super(MailMessage, self)._non_employee_message_domain()
+        return expression.AND([domain, [('website_published', '=', True)]])
+
     @api.multi
     def _compute_description(self):
         for message in self: