1) Check if your internet connection is active, and if you can access your email (http://www.yourdomain.com/webmail or http://webmail.yourdomain.com if you are using cPanel)
2) Can you access your control panel? Check if your email account is not full.
3) In last resort, you can open a support ticket by providing the following:
-Your domain name, specific email account having the issue, and details on the issue (such as error messages received when sending out/receiving)
-Your IP address (which you can find by going to www.myipaddress.com)
