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Tools

DNS Lookup Look up A, AAAA, MX, TXT, NS, CAA and other records, from a public resolver or straight from the authoritative nameservers.
DNSSEC Checker Follow the chain of trust from the parent DS record to the zone's DNSKEY and signatures, and see what validating resolvers conclude.
Nameserver Check Compare the nameservers set at the registry with what the authoritative servers report, and check each server responds correctly.
SSL Certificate Checker Check whether a site serves HTTPS, when its certificate expires, whether browsers will trust it, and how HTTP traffic is redirected.
SPF, DKIM & DMARC Checker Check SPF, DKIM and DMARC: the records inboxes use to decide whether your mail is genuine, and whether they are strict enough to stop spoofing.
DNS Propagation Checker Compare what public resolvers around the world currently return with the authoritative answer, and see how long cached data will last.
Subdomain Finder Pro List a domain's subdomains and find the ones exposed to a takeover through a forgotten alias.
WHOIS Lookup See who a domain is registered with, when it was registered and expires, and whether it is locked against theft, straight from the registry.
Email Blacklist Check Emails landing in spam? See whether your mail server or domain is on a spam blacklist that mail providers check, why it was listed, and how to get removed.

Not sure where to start? Run them in order, from records to email. How the checks work

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Tools

DNS Lookup
DNSSEC Checker
Nameserver Check
SSL Certificate Checker
SPF, DKIM & DMARC Checker
DNS Propagation Checker
Subdomain Finder Pro
WHOIS Lookup
Email Blacklist Check

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Tools/SSL Certificate Checker

SSL Certificate Checker

Domain Port

Checking expired.badssl.com

Resolving the hostname…

d.dnsdon

Free, read-only DNS diagnostics. Every finding is based on live query results, and every query is listed so you can reproduce it.

Tools

DNS Lookup DNSSEC Checker Nameserver Check SSL Certificate Checker SPF, DKIM & DMARC Checker DNS Propagation Checker Subdomain Finder WHOIS Lookup Email Blacklist Check

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