diff --git a/addons/mail/mail_thread.py b/addons/mail/mail_thread.py
index 3103e4da298..6a32ed3bb52 100644
--- a/addons/mail/mail_thread.py
+++ b/addons/mail/mail_thread.py
@@ -101,12 +101,16 @@ class mail_thread(osv.AbstractModel):
 
         if catchall_domain and model and res_id:  # specific res_id -> find its alias (i.e. section_id specified)
             object_id = self.pool.get(model).browse(cr, uid, res_id, context=context)
-            alias = object_id.alias_id
+            # check that the alias effectively creates new records
+            if object_id.alias_id and object_id.alias_id.alias_model_id and \
+                    object_id.alias_id.alias_model_id.model == self._name and \
+                    object_id.alias_id.alias_force_thread_id == 0:
+                alias = object_id.alias_id
         elif catchall_domain and model:  # no specific res_id given -> generic help message, take an example alias (i.e. alias of some section_id)
             model_id = self.pool.get('ir.model').search(cr, uid, [("model", "=", self._name)], context=context)[0]
             alias_obj = self.pool.get('mail.alias')
-            alias_ids = alias_obj.search(cr, uid, [("alias_model_id", "=", model_id)], context=context, limit=1, order='id ASC')
-            if alias_ids:
+            alias_ids = alias_obj.search(cr, uid, [("alias_model_id", "=", model_id), ('alias_force_thread_id', '=', 0)], context=context, order='id ASC')
+            if alias_ids and len(alias_ids) == 1:  # if several aliases -> incoherent to propose one guessed from nowhere, therefore avoid if several aliases
                 alias = alias_obj.browse(cr, uid, alias_ids[0], context=context)
 
         if alias: