Checking what is actually published.
WHAT THEY DO
Query DNS and show what is returned, without your own device's cache in the way.
WHAT TO CHECK
A records, for where the site points MX records, for mail TXT records, for SPF, DKIM and verification NS records, for which nameservers are authoritative
QUERYING AUTHORITATIVELY
The most useful capability. Ask your own nameservers directly rather than a cached resolver.
That distinguishes a change that has not been made from one that is propagating.
FROM SEVERAL LOCATIONS
Tools that query from multiple places show how far a change has spread.
Useful during a migration.
ON YOUR OWN MACHINE
Command line tools query DNS directly and are faster than any web interface once you know them.
WHAT TO LOOK FOR
Records present and correct Exactly one SPF record MX records pointing at a hostname that itself resolves No conflicting records for the same name
THE HABIT WORTH BUILDING
Check DNS before assuming a problem is elsewhere. It takes thirty seconds and eliminates a whole category of cause.
