diff --git a/odoo/tools/mail.py b/odoo/tools/mail.py
index cff0779a658..e1a4eeb9c54 100644
--- a/odoo/tools/mail.py
+++ b/odoo/tools/mail.py
@@ -436,7 +436,7 @@ def generate_tracking_message_id(res_id):
     except NotImplementedError:
         rnd = random.random()
     rndstr = ("%.15f" % rnd)[2:]
-    return "<%.15f.%s-openerp-%s@%s>" % (time.time(), rndstr, res_id, socket.gethostname())
+    return "<%s.%.15f-openerp-%s@%s>" % (rndstr, time.time(), res_id, socket.gethostname())
 
 def email_send(email_from, email_to, subject, body, email_cc=None, email_bcc=None, reply_to=False,
                attachments=None, message_id=None, references=None, openobject_id=False, debug=False, subtype='plain', headers=None,