DE EN IT

~/tools / mail-dns-checker

Mail DNS checker

Mail not arriving or landing in spam? See at a glance which DNS records are missing.

daniele@mikweb: ~/tools — less mail-dns-checker.md

What is checked

  • MX: are there mail servers, and do they have addresses?
  • Reverse DNS (PTR): does each address point to a name that points back to the same address? Many receivers reject otherwise.
  • SPF and DMARC: present, unique, policy set?
  • MTA-STS and TLS-RPT: enforce encrypted delivery and report problems.

How well do big domains protect their mail?

The e-mail ranking shows SPF, DMARC and MTA-STS of about 100 well-known domains, with a live check on every row.

Privacy

The domain or address you enter is sent to this server, which runs the check. Nothing is stored; to prevent abuse a salted hash of your IP address is kept for one hour. Only public addresses are queried.

daniele@mikweb: ~/blog — ls

Related articles

Mail landing in spam: SPF, DKIM and DMARC alignment explainedSPF, DKIM and DMARC explained simply: what each checks, why mail lands in spam although SPF passes, how to read headers — with a table and checklist.
daniele@mikweb: ~/tools — ls

Tools

SPF checkerCounts the DNS lookups of your SPF record (limit: 10).DNS TTL plannerPlans the TTL reduction and the move time.Cron explainerExplains cron expressions and shows the next runs.DMARC generatorBuilds a valid DMARC record to copy.Certificate checkExpiry, chain and names of a TLS certificate.Security headersGrades HSTS, CSP and other security headers.JWT decoderShows header, claims and expiry of a JWT — in your browser only.SAML decoderDecodes SAML responses and spots typical errors.nginx for NextcloudGenerates an nginx config for Nextcloud with PHP-FPM.Explain an errorPaste an error — meaning, causes and checks (AI).Base64 encode/decodeEncode and decode Base64, files and Basic-auth headers included — in your browser only.chmod calculatorFile permissions octal ↔ symbolic, ready chmod commands and umask — in your browser only.Subnet calculatorWorks out CIDR, netmask, wildcard and hosts for IPv4 and IPv6 and splits networks into subnets.Epoch converterConvert Unix timestamps to dates and back, with time zones and a year-2038 check — in your browser only.Hash generatorSHA-256, SHA-512, SHA-1 and MD5 for text and files, with HMAC and a compare field — in your browser only.JSON formatterFormat, minify, sort and validate JSON, with errors shown by line and column — in your browser only.Password generatorRandom passwords and passphrases with an entropy readout — generated in your browser only.Redirect generatorGenerates redirects for nginx and Apache (.htaccess) with a curl test.

← Tools