Domain contact validation and verification is required per ICANN bylaws. Registering a domain will result in a verification email being sent to the primary contact for the domain, and will have a tokenized link at http://approve.domainadmin.com. Existing domains can also be chose at random for verification, and the verification email will also have a link at this URL. Clicking through the link in the email and clicking the verify button on the resulting page is required. Failure to validate a domain will result in the registrar placing the domain on hold until the domain in validated. This will cause all functions associated with the domain to stop functioning, including mail.
If a domain stops functioning, but is not expired, it is possible the domain is on hold. Contact support for assistance with domains that are not working properly. We will be able to determine the cause and work with you to take the stps necessary to return the domain to operation.