What does this post have to do with Zimbra Desktop which is the forum in which you've posted? I'll move this to the correct forum.
First thing to mention, the reason you're admin didn't receive the mail is that you are using the wrong domain name, it should be: admin@wantedstanding.com What you've used is a subdomain and I'm guessing you have "mail.wantedstanding.com" as the primary domain on your server.
Telling us you have "valid MX records" doesn't really tell us anything and without the exact details of your domain name and the resulting output from the relevant dig commands would tell us whether they're correct, or not. ;)r