CNAME lookup
See whether a domain is an alias that points on to another domain.
About CNAME lookup
What it is
A CNAME record (Canonical Name) makes a domain or subdomain an alias for another. Instead of pointing to an IP address, it points to another domain name.
Why it matters
CNAME is often used for subdomains such as mail.company.com or www.company.com. An incorrect CNAME can route traffic entirely wrong, and a CNAME on the root domain (without www) is not allowed by the standard.
Tips
- Never set a CNAME on the root domain (company.com), only on subdomains.
- Chains of CNAMEs are allowed but should be minimised for faster resolution.
- If a service requires CNAME pointers, check that they are still current.
Common questions
Can I have a CNAME on company.com (without www)?
No, the standard does not allow a CNAME on the root domain because MX and NS records cannot coexist with a CNAME.
What happens if the CNAME chain is broken?
Visitors and systems cannot reach your domain at all, or end up on an error page. Every link in the chain must point correctly.
More lookups
MX lookup
See which servers receive mail for a domain, and which provider handles it.
SPF check
Check whether a domain has an SPF record and how strictly it rejects spoofed mail.
DMARC check
See whether a domain has DMARC and which policy it uses against spoofed mail.
DKIM check
Look for DKIM signing on a domain using the most common selectors.
DNSSEC check
See whether a domain is protected with DNSSEC, that is, whether its DNS answers are signed.
TXT lookup
List all TXT records for a domain, including SPF, verifications and more.
NS lookup
See which name servers control a domain's DNS.
Blacklist check
Check whether a domain's IP address is on blacklists such as Spamhaus, Barracuda and SpamCop.
A/AAAA lookup
See which IP addresses a domain points to, both IPv4 (A) and IPv6 (AAAA).
SOA lookup
See the zone's core data: primary name server, contact and serial number.
CAA lookup
See which certificate authorities are allowed to issue certificates for the domain.
Reverse DNS (PTR)
Look up which host name a domain's IP address points back to.
MTA-STS
See whether a domain requires encrypted mail delivery via MTA-STS.
TLS-RPT
See whether a domain receives reports about failed encrypted mail delivery.
BIMI
See whether a domain publishes a logo that can be shown in the recipient's inbox.
SSL certificate
Check a domain's TLS certificate: issuer, validity and expiry.
Whois
See who owns a domain, when it was registered and when it expires.
HTTP security headers
Check whether a domain's website sets important security headers.