Check your mail setup, DNS records and certificates in seconds. No sign-up, nothing stored, and every result says what it could not check.
Most email and certificate problems have small causes. A mail provider is added and SPF goes over its lookup limit. A certificate is renewed but the intermediate is left out. A DMARC record is published at monitoring only and never tightened. None of these shows an error anywhere; mail goes to spam, a mobile app stops connecting, someone spoofs your domain. These tools read what a domain publishes, say what is wrong in plain language, and say what they could not check, so a missing answer is never mistaken for a good one.
Almost everything here reads public DNS, which anyone can query. The SSL checker opens a single TLS connection to the server you name, the way a browser does, and reads the certificate chain. The blacklist check asks public DNS blocklists about an address. The header analyser reads the text you paste and never looks anything up. Nothing is stored, nothing is sent to a third party, and no email is ever sent. Requests are limited per visitor so the tools stay fast for everyone.
If mail is the problem, begin with the email health check: it reads MX, SPF, DKIM, DMARC, MTA-STS and blocklists together, then use the individual tools to dig into whichever area failed. If a certificate warning is the problem, the SSL checker shows the chain, the names and the expiry, and usually points at the cause. If a message looks suspicious, paste its header into the analyser to see where it came from and whether it authenticated.
These tools look at one domain from the outside. For one report that combines the domain, mail, certificates, your website and public exposure into a single score, run the cybersecurity posture review. For configuration they cannot see, such as firewalls and cloud accounts, there are separate reviews, and a practitioner can take it from there.