Starting January 1st, 2014, a new ICANN rule will require that domain name owners/registrants verify their email address within 15 days of a change to the contact name or email.
Domain name registrants will now need to verify that the email address provided during registration is active and can receive email. This will be done by clicking on an verification link within the email. Registrants (domain administrators) will only need to this once per contact, so in essence, a contact can be used on several domains without the need for multiple verification emails.
Should you opt to ignore that message your website or email could stop working entirely so this is quite important to be in the loop on. Sites that don't undergo verfication will see their websites replaced with the equivalent of a parked or placeholder page.
The new rule is part of ICANN’s Registrar Accreditation Agreement that was approved earlier this year (2013) and will affect all domain registrars and resellers.