Make sure your have turn on the mail rescue mode while your mail server is down. In this case, emails going to your domain should end up at our mail rescue server.
To access your email through POP3 client, you can point the POP3 server to mailrescue.dnsexit.com. The login to the POP server is your email address in lower case. The password is the password for the email address while you create the email at mail resuce server. If you don't remember the password, go to Backup MX Panel for the domain, click on "Manage" for the Mail Rescue Mail Boxes, you will see the password shown as ***** but it is a link that you can click to show the password.
You can also access your emails with web mail at webmail2.dnsexit.com with the login/password mention above.