[FIX] write can be multi

mail_tracking/models/mail_bounced_mixin.py

@@ -31,8 +31,9 @@ class MailBouncedMixin(models.AbstractModel):
         partners = self.filtered(lambda r: not r.email_bounced)
         return partners.write({'email_bounced': True})
 
+    @api.multi
     def write(self, vals):
-        [email_field] = self._primary_email
+        [email_field] = self[0]._primary_email
         if email_field not in vals:
             return super().write(vals)
         email = vals[email_field].lower() if vals[email_field] else False