diff --git a/addons/purchase/models/__init__.py b/addons/purchase/models/__init__.py
index e90a45dff29..dead81bb8fb 100644
--- a/addons/purchase/models/__init__.py
+++ b/addons/purchase/models/__init__.py
@@ -2,7 +2,6 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
 import account_invoice
-import mail_mail
 import purchase
 import res_company
 import res_config
diff --git a/addons/purchase/models/mail_mail.py b/addons/purchase/models/mail_mail.py
deleted file mode 100644
index 433ff1d66a5..00000000000
--- a/addons/purchase/models/mail_mail.py
+++ /dev/null
@@ -1,18 +0,0 @@
-# -*- coding: utf-8 -*-
-# Part of Odoo. See LICENSE file for full copyright and licensing details.
-
-from odoo import api, models
-
-
-class MailMail(models.Model):
-    _name = 'mail.mail'
-    _inherit = 'mail.mail'
-
-    @api.multi
-    def _postprocess_sent_message(self, mail_sent=True):
-        for mail in self:
-            if mail_sent and mail.model == 'purchase.order':
-                purchase_order = self.env['purchase.order'].browse(mail.res_id)
-                if purchase_order.state == 'draft':
-                    self.env['purchase.order'].signal_workflow([mail.res_id], 'send_rfq')
-        return super(MailMail, self)._postprocess_sent_message(mail_sent=mail_sent)