When registering a new domain, transferring a domain name (applies to top-level domains managed by ICANN), or changing the email address on an existing domain, you must confirm that the email address provided as the contact is valid. An email is sent out automatically with the following message:
"Dear registrant or prospective registrant, due to the requirements under the ICANN Registrar Accreditation Agreement we are required to confirm the validity of the email address provided for the domain name registration application or contact creation. The domain(s) listed below were registered/updated with your e-mail address in the domain owner contact. It is now mandatory that you confirm the accessibility of your email address…"
You must verify this by clicking the link in the email. If you don't, your domain will stop working. ICANN requires that the email address for a domain name is validated before it can be approved. If you haven't received the email, it may have ended up in your spam folder — make sure to check there.
When placing an order or initiating a transfer, you as the customer are solely responsible if a domain is suspended due to an unvalidated email address, and for any deregistration of the domain that may result from this.