diff --git a/addons/mail/models/mail_thread.py b/addons/mail/models/mail_thread.py
index 3fee0e1b7cc..072a76da4c8 100644
--- a/addons/mail/models/mail_thread.py
+++ b/addons/mail/models/mail_thread.py
@@ -947,11 +947,14 @@ class MailThread(models.AbstractModel):
 
         # Alias: check alias_contact settings
         if alias:
-            if alias.alias_parent_model_id and alias.alias_parent_thread_id:
+            obj = None
+            if thread_id:
+                obj = record_set[0]
+            elif alias.alias_parent_model_id and alias.alias_parent_thread_id:
                 obj = self.env[alias.alias_parent_model_id.model].browse(alias.alias_parent_thread_id)
-            elif model and hasattr(record_set, '_alias_check_contact'):
-                obj = record_set[0] if thread_id else self.env[model]
-            else:
+            elif model:
+                obj = self.env[model]
+            if not hasattr(obj, '_alias_check_contact'):
                 obj = self.env['mail.alias.mixin']
             check_result = obj._alias_check_contact(message, message_dict, alias)
             if check_result is not True: