Parked and held domains.
THE SITUATION
A domain registered for future use, or defensively, with no site yet.
WHAT TO DO
Nothing is required. A registered domain with no DNS simply does not resolve.
WHAT IS BETTER
Point it somewhere sensible: a redirect to your main site, or a simple holding page.
A domain resolving to nothing looks abandoned; a redirect looks deliberate.
SETTING UP A REDIRECT
Add it to your hosting as an alias with a redirect, or use a redirect rule at your DNS provider if it offers one.
A domain with no MX records receives no mail. Usually correct for a held domain.
If you want mail to it, add MX records and a forwarder.
WHAT TO WATCH
The renewal date. A defensively registered domain is easy to forget and losing it defeats the purpose.
Enable auto-renewal.
SECURITY
Someone can send mail claiming to be from a domain with no SPF record.
Publishing an SPF record permitting nothing, on a domain that sends no mail, prevents impersonation.
That is worth doing for held domains.
