1. General Results, most used to calculate the result A name "tc.apple.com" is subdomain, public suffix is ".com", top-level-domain is ".com", top-level-domain-type is "generic", tld-manager is "VeriSign Global Registry Services", num .com-domains preloaded: 85538 (complete: 220007) A Good: No asked Authoritative Name Server had a timeout HSTS-Preload-Status: unknown. Domain never included in the Preload-list. Check https://hstspreload.org/ to learn some basics about the Google-Preload-List. A Good: _mta-sts TXT record found (mta-sts: Mail Transfer Agent Strict Transport Security - see RFC 8461). Domainname: _mta-sts.tc.apple.com B Bad: _mta-sts TXT found, but invalid 2. Header-Checks (alpha, started 2022-10-23, may be buggy / incomplete) U No https result with http status 2** or 4** (standard-check) found, no header checked. 3. DNS- and NameServer - Checks A Info:: 2 Root-climbing DNS Queries required to find all IPv4- and IPv6-Addresses of 4 Name Servers. A Info:: 2 Queries complete, 2 with IPv6, 0 with IPv4. A Good: All DNS Queries done via IPv6. A Good: Some ip addresses of name servers found with the minimum of two DNS Queries. One to find the TLD-Zone, one to ask the TLD-Zone.a.ns.apple.com (17.253.200.1, 2620:149:ae0::53), b.ns.apple.com (17.253.207.1, 2620:149:ae7::53), c.ns.apple.com (204.19.119.1, 2620:171:800:714::1), d.ns.apple.com (204.26.57.1, 2620:171:801:714::1) A Good (1 - 3.0):: An average of 0.5 queries per domain name server required to find all ip addresses of all name servers. A Info:: 5 different Name Servers found: a.ns.apple.com, b.ns.apple.com, c.ns.apple.com, d.ns.apple.com, usmsc2-extxfr-001.dns.apple.com, 4 Name Servers included in Delegation: a.ns.apple.com, b.ns.apple.com, c.ns.apple.com, d.ns.apple.com, 4 Name Servers included in 2 Zone definitions: a.ns.apple.com, b.ns.apple.com, c.ns.apple.com, d.ns.apple.com, 1 Name Servers listed in SOA.Primary: usmsc2-extxfr-001.dns.apple.com. A Good: Only one SOA.Primary Name Server found.: usmsc2-extxfr-001.dns.apple.com. Error: SOA.Primary Name Server not included in the delegation set.: usmsc2-extxfr-001.dns.apple.com. A Good: Consistency between delegation and zone. The set of NS records served by the authoritative name servers must match those proposed for the delegation in the parent zone. Ordered list of name servers: a.ns.apple.com, b.ns.apple.com, c.ns.apple.com, d.ns.apple.com A Good: All Name Server Domain Names have a Public Suffix. Error: Name Server Domain Names with Public Suffix and without ip address found.: 1 Name Servers without ipv4 and ipv6: 1 A Good: Minimal 2 different name servers (public suffix and public ip address) found: 4 different Name Servers found A Good: All name servers have ipv4- and ipv6-addresses.: 4 different Name Servers found Warning: All Name Servers have the same Top Level Domain / Public Suffix. If there is a problem with that Top Level Domain, your domain may be affected. Better: Use Name Servers with different top level domains.: 4 Name Servers, 1 Top Level Domain: com Warning: All Name Servers have the same domain name. If there is a problem with that domain name (or with the name servers of that domain name), your domain may be affected. Better: Use Name Servers with different domain names / different top level domains.: Only one domain name used: apple.com A Good: Name servers with different Country locations found: 4 Name Servers, 2 Countries: CA, US A Info: Ipv4-Subnet-list: 4 Name Servers, 2 different subnets (first Byte): 17., 204., 3 different subnets (first two Bytes): 17.253., 204.19., 204.26., 4 different subnets (first three Bytes): 17.253.200., 17.253.207., 204.19.119., 204.26.57. A Good: Name Server IPv4-addresses from different subnet found: A Info: IPv6-Subnet-list: 4 Name Servers with IPv6, 1 different subnets (first block): 2620:, 2 different subnets (first two blocks): 2620:0149:, 2620:0171:, 4 different subnets (first three blocks): 2620:0149:0ae0:, 2620:0149:0ae7:, 2620:0171:0800:, 2620:0171:0801:, 4 different subnets (first four blocks): 2620:0149:0ae0:0000:, 2620:0149:0ae7:0000:, 2620:0171:0800:0714:, 2620:0171:0801:0714: A Good: Name Server IPv6 addresses from different subnets found. A Good: Nameserver supports TCP connections: 1 good Nameserver A Good: Nameserver supports Echo Capitalization: 1 good Nameserver A Good: Nameserver supports EDNS with max. 512 Byte Udp payload, message is smaller: 1 good Nameserver A Good: Nameserver has passed 10 EDNS-Checks (OP100, FLAGS, V1, V1OP100, V1FLAGS, DNSSEC, V1DNSSEC, NSID, COOKIE, CLIENTSUBNET): 1 good Nameserver Nameserver doesn't pass all EDNS-Checks: usmsc2-extxfr-001.dns.apple.com: OP100: no result. FLAGS: no result. V1: no result. V1OP100: no result. V1FLAGS: no result. DNSSEC: no result. V1DNSSEC: no result. NSID: no result. COOKIE: no result. CLIENTSUBNET: no result. Nameserver doesn't pass all EDNS-Checks: usmsc2-extxfr-001.dns.apple.com: OP100: no result. FLAGS: no result. V1: no result. V1OP100: no result. V1FLAGS: no result. DNSSEC: no result. V1DNSSEC: no result. NSID: no result. COOKIE: no result. CLIENTSUBNET: no result. A Good: All SOA have the same Serial Number A Good: CAA entries found, creating certificate is limited: entrust.net is allowed to create certificates A Good: CAA entries found, creating certificate is limited: pki.apple.com is allowed to create certificates 4. Content- and Performance-critical Checks A Good: Domainname is not on the "Specially Designated Nationals And Blocked Persons List" (SDN). That's an US-list of individuals and companies owned or controlled by, or acting for or on behalf of, targeted countries. It also lists individuals, groups, and entities, such as terrorists and narcotics traffickers designated under programs that are not country-specific. Collectively, such individuals and companies are called "Specially Designated Nationals" or "SDNs." Their assets are blocked and U.S. persons are generally prohibited from dealing with them. So if a domain name is on that list, it's impossible to create a Letsencrypt certificate with that domain name. Check the list manual - https://www.treasury.gov/resource-center/sanctions/sdn-list/pages/default.aspx A Duration: 93737 milliseconds, 93.737 seconds