Which CAs may issue certificates
DNS & Records
DNS Lookup Every DNS record for any domain A Record Lookup IPv4 addresses for a domain AAAA Record Lookup IPv6 addresses for a domain MX Lookup Mail servers for a domain NS Lookup Authoritative name servers TXT Lookup TXT records, SPF, verification CNAME Lookup Canonical name (alias) records SOA Lookup Start of Authority record SRV Lookup Service location records CAA Lookup Which CAs may issue certificates Reverse DNS (PTR) IP address to hostname DNSSEC Check Is the domain signed and validated?Email Deliverability
SPF Check Validate your Sender Policy Framework record DMARC Check Inspect and grade your DMARC policy DKIM Check Find and validate your DKIM public key Blacklist Check Check an IP against email blocklists (DNSBLs) SMTP Test Connect to a mail server and check STARTTLS MTA-STS Check Enforced TLS policy for inbound mail BIMI Check Brand logo record for email TLS-RPT Check SMTP TLS reporting policyNetwork & Web
SSL Certificate Check Inspect a site's TLS certificate and expiry HTTP Header Check Inspect response headers, redirects and security Ping (TCP) Reachability and latency over TCP Port Check Which common ports are openDomain
WHOIS Lookup Registration data for domains, IPs and ASNsCAA (Certification Authority Authorization) records let a domain declare which certificate authorities may issue certificates for it. CAs are required to honour them, reducing the risk of mis-issuance.