When something is seriously wrong.
THE DOMAIN DOES NOT RESOLVE AT ALL
Check expiry first. An expired domain is the most common cause and the most time-sensitive.
Open a ticket immediately.
MAIL HAS STOPPED
Check MX records and the hostname they point at.
Check the cPanel email routing setting.
Those two account for nearly every case.
THE SITE POINTS SOMEWHERE WRONG
Check where DNS lives, then check the A record there.
If someone else changed it, treat it as a security incident.
NAMESERVERS CHANGED WITHOUT YOU DOING IT
A registrar account compromise, or an unauthorised transfer.
Contact the registrar immediately and change credentials.
DNSSEC MISMATCH
The domain fails to resolve entirely for validating resolvers.
Disable DNSSEC, or correct the DS record.
WHAT TO HAVE READY
Your zone export Registrar and DNS provider credentials, accessible without the domain working A contact address on another domain
THE LAST POINT MATTERS
If your only email is on the affected domain, you cannot receive the notifications you need.
