diff --git a/addons/portal/mail_message.py b/addons/portal/mail_message.py
index 38516268c24..d0a4db5853e 100644
--- a/addons/portal/mail_message.py
+++ b/addons/portal/mail_message.py
@@ -33,9 +33,9 @@ class mail_message(osv.Model):
             all no discussion message if uid is a portal user.
         """
         group_ids = self.pool.get('res.users').browse(cr, uid, uid, context=context).groups_id
-        if any(group.is_portal for group in group_ids):
-            subtype_id = self.pool.get("ir.model.data").get_object_reference(cr, uid, 'mail', 'mt_comment')[1]
-            args = ['&', ('subtype_id', '=', subtype_id)] + args
+        group_user_id = self.pool.get("ir.model.data").get_object_reference(cr, uid, 'base', 'group_user')[1]
+        if group_user_id not in [group.id for group in group_ids]:
+            args = ['&', '|', ('type', '!=', 'comment'), ('subtype_id', '!=', False)] + list(args)
 
         return super(mail_message, self)._search(cr, uid, args, offset=offset, limit=limit, order=order,
             context=context, count=False, access_rights_uid=access_rights_uid)
@@ -46,9 +46,9 @@ class mail_message(osv.Model):
                 - raise if the type is not 'comment' or 'email'
         """
         group_ids = self.pool.get('res.users').browse(cr, uid, uid, context=context).groups_id
-        if any(group.is_portal for group in group_ids):
-            subtype_id = self.pool.get("ir.model.data").get_object_reference(cr, uid, 'mail', 'mt_comment')[1]
-            cr.execute('SELECT DISTINCT id FROM "%s" WHERE subtype_id != %s AND id = ANY (%%s)' % (self._table, subtype_id), (ids,))
+        group_user_id = self.pool.get("ir.model.data").get_object_reference(cr, uid, 'base', 'group_user')[1]
+        if group_user_id not in [group.id for group in group_ids]:
+            cr.execute('SELECT DISTINCT id FROM "%s" WHERE type = %%s AND subtype_id != NULL AND id = ANY (%%s)' % (self._table), ('comment', ids,))
             if cr.fetchall():
                 raise orm.except_orm(_('Access Denied'),
                         _('The requested operation cannot be completed due to security restrictions. Please contact your system administrator.\n\n(Document type: %s, Operation: %s)') % \
diff --git a/addons/portal/tests/test_portal.py b/addons/portal/tests/test_portal.py
index 03f2491315b..1cfb2aef269 100644
--- a/addons/portal/tests/test_portal.py
+++ b/addons/portal/tests/test_portal.py
@@ -40,7 +40,9 @@ class test_portal(TestMailBase):
         self.partner_chell_id = self.user_chell.partner_id.id
 
         # Create a PigsPortal group
-        self.group_port_id = self.mail_group.create(cr, uid, {'name': 'PigsPortal', 'public': 'groups', 'group_public_id': self.group_portal_id})
+        self.group_port_id = self.mail_group.create(cr, uid,
+                        {'name': 'PigsPortal', 'public': 'groups', 'group_public_id': self.group_portal_id},
+                        {'mail_create_nolog': True})
 
         # Set an email address for the user running the tests, used as Sender for outgoing mails
         self.res_users.write(cr, uid, uid, {'email': 'test@localhost'})
@@ -130,3 +132,21 @@ class test_portal(TestMailBase):
                             'body of invitation email is incorrect')
             self.assertTrue(partner_carine.signup_url in sent_email.get('body'),
                             'body of invitation email does not contain signup url')
+
+    def test_20_message_read(self):
+        cr, uid, group_port_id = self.cr, self.uid, self.group_port_id
+
+        # Data: custom subtypes
+        mt_group_public_id = self.mail_message_subtype.create(cr, uid, {'name': 'group_public', 'description': 'Group changed'})
+        self.ir_model_data.create(cr, uid, {'name': 'mt_group_public', 'model': 'mail.message.subtype', 'module': 'mail', 'res_id': mt_group_public_id})
+        # Data: post messages with various subtypes
+        msg1_id = self.mail_group.message_post(cr, uid, group_port_id, body='Body1', type='comment', subtype='mail.mt_comment')
+        msg2_id = self.mail_group.message_post(cr, uid, group_port_id, body='Body2', type='comment', subtype='mail.mt_group_public')
+        msg3_id = self.mail_group.message_post(cr, uid, group_port_id, body='Body3', type='comment', subtype='mail.mt_comment')
+        msg4_id = self.mail_group.message_post(cr, uid, group_port_id, body='Body4', type='comment')
+        msg5_id = self.mail_group.message_post(cr, uid, group_port_id, body='Body5', type='notification')
+
+        # Do: Chell search messages: should not see internal notes (comment without subtype)
+        msg_ids = self.mail_message.search(cr, self.user_chell_id, [('model', '=', 'mail.group'), ('res_id', '=', group_port_id)])
+        self.assertEqual(set(msg_ids), set([msg1_id, msg2_id, msg3_id, msg5_id]),
+                        'mail_message: portal user has access to messages he should not read')