1. General Results, most used to calculate the result A name "api.bebook.vn" is subdomain, public suffix is ".vn", top-level-domain is ".vn", top-level-domain-type is "country-code", Country is Viet Nam, tld-manager is "Ministry of Information and Communications of Socialist Republic of Viet Nam", num .vn-domains preloaded: 301 (complete: 221801) A Good: All ip addresses are public addresses Warning: Only one ip address found: api.bebook.vn has only one ip address. Warning: No ipv6 address found. Ipv6 is the future with a lot of new features. So every domain name should have an ipv6 address. See https://en.wikipedia.org/wiki/IPv6: api.bebook.vn has no ipv6 address. A DNS: "Name Error" means: No www-dns-entry defined. This isn't a problem A Good: No cookie sent via http. 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: Some urls with http status 200/404 have a complete Content-Type header (MediaType / MediaSubType + correct charset):1 complete Content-Type - header (3 urls) http://api.bebook.vn/ 18.140.165.202 Url with incomplete Content-Type - header - missing charset http://api.bebook.vn:443/ 18.140.165.202 Url with incomplete Content-Type - header - missing charset H Fatal error: No https - result with http-status 200, no encryption H Fatal error: http result with http-status 200, no encryption. Add a redirect http ⇒ https, so every connection is secure. Perhaps in your port 80 vHost something like "RewriteEngine on" + "RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,QSA,R=permanent]" (two rows, without the "). Don't add this in your port 443 vHost, that would create a loop. Q http://api.bebook.vn:443/ 18.140.165.202 Misconfiguration: http sent over port 443. Wrong port forwarding port 443 to port 80 or wrong vHost definition. If you use a virtual Host <VirtualHost ip-address:443>, try <VirtualHost *:443>. X Fatal error: Nameserver doesn't support TCP connection: ns1.zonedns.vn / 2401:5f80:2001:5::a: Timeout X Fatal error: Nameserver doesn't support TCP connection: ns2.zonedns.vn / 2401:5f80:2001:5::a: Timeout Info: Checking the ip addresses of that domain name not exact one certificate found. So it's impossible to check if that domain requires Server Name Indication (SNI).: Domain api.bebook.vn, 1 ip addresses. B No _mta-sts TXT record found (mta-sts: Mail Transfer Agent Strict Transport Security - see RFC 8461). Read the result of server-daten.de (Url-Checks, Comments, Connections and DomainServiceRecords) to see a complete definition. Domainname: _mta-sts.api.bebook.vn 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:: 13 Root-climbing DNS Queries required to find all IPv4- and IPv6-Addresses of 4 Name Servers. A Info:: 13 Queries complete, 5 with IPv6, 8 with IPv4. Warning: Only some DNS Queries done via ipv6. IPv6 is the future, so the name servers of your name servers should have ipv6 addresses. Ok (4 - 8):: An average of 3.3 queries per domain name server required to find all ip addresses of all name servers. A Info:: 4 different Name Servers found: ns1.zonedns.vn, ns2.zonedns.vn, ns3.zonedns.vn, ns4.zonedns.vn, 4 Name Servers included in Delegation: ns1.zonedns.vn, ns2.zonedns.vn, ns3.zonedns.vn, ns4.zonedns.vn, 4 Name Servers included in 1 Zone definitions: ns1.zonedns.vn, ns2.zonedns.vn, ns3.zonedns.vn, ns4.zonedns.vn, 1 Name Servers listed in SOA.Primary: ns1.zonedns.vn. A Good: Only one SOA.Primary Name Server found.: ns1.zonedns.vn. A Good: SOA.Primary Name Server included in the delegation set.: ns1.zonedns.vn. 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: ns1.zonedns.vn, ns2.zonedns.vn, ns3.zonedns.vn, ns4.zonedns.vn A Good: All Name Server Domain Names have a Public Suffix. A Good: All Name Server Domain Names ending with a Public Suffix have minimal one IPv4- or IPv6 address. A Good: All Name Server ip addresses are public. 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: vn 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: zonedns.vn Warning: All Name Servers from the same Country / IP location.: 4 Name Servers, 1 Countries: VN A Info: Ipv4-Subnet-list: 4 Name Servers, 2 different subnets (first Byte): 103., 125., 3 different subnets (first two Bytes): 103.176., 103.28., 125.212., 4 different subnets (first three Bytes): 103.176.178., 103.28.36., 103.28.39., 125.212.225. A Good: Name Server IPv4-addresses from different subnet found: A Info: IPv6-Subnet-list: 4 Name Servers with IPv6, 2 different subnets (first block): 2001:, 2401:, 2 different subnets (first two blocks): 2001:0df1:, 2401:5f80:, 2 different subnets (first three blocks): 2001:0df1:3200:, 2401:5f80:2001:, 2 different subnets (first four blocks): 2001:0df1:3200:0000:, 2401:5f80:2001:0005: A Good: Name Server IPv6 addresses from different subnets found. A Good: Nameserver supports TCP connections: 2 good Nameserver A Good: Nameserver supports Echo Capitalization: 2 good Nameserver X Nameserver Timeout checking Echo Capitalization: e.dns-servers.vn X Nameserver Timeout checking Echo Capitalization: ns2.zonedns.vn / 2401:5f80:2001:5::a A Good: Nameserver supports EDNS with max. 512 Byte Udp payload, message is smaller: 2 good Nameserver X Nameserver Timeout checking EDNS512: ns2.zonedns.vn / 2401:5f80:2001:5::a Nameserver doesn't pass all EDNS-Checks: dns-master.vnnic.vn: 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: h.dns-servers.vn: OP100: ok. FLAGS: ok. V1: ok. V1OP100: ok. V1FLAGS: ok. DNSSEC: ok. V1DNSSEC: ok. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns1.zonedns.vn: 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: ns1.zonedns.vn / 2401:5f80:2001:5::a: OP100: ok. FLAGS: ok. V1: ok. V1OP100: ok. V1FLAGS: ok. DNSSEC: fatal timeout. V1DNSSEC: ok. NSID: fatal timeout. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns1.zonedns.vn / 2401:5f80:2001:5::a: OP100: ok. FLAGS: ok. V1: ok. V1OP100: ok. V1FLAGS: ok. DNSSEC: ok. V1DNSSEC: ok. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. Nameserver doesn't pass all EDNS-Checks: ns2.zonedns.vn / 2401:5f80:2001:5::a: OP100: ok. FLAGS: fatal timeout. V1: fatal timeout. V1OP100: fatal timeout. V1FLAGS: ok. DNSSEC: ok. V1DNSSEC: ok. NSID: ok. COOKIE: ok. CLIENTSUBNET: ok. A Good: All SOA have the same Serial Number Warning: No CAA entry with issue/issuewild found, every CAA can create a certificate. Read https://en.wikipedia.org/wiki/DNS_Certification_Authority_Authorization to learn some basics about the idea of CAA. Your name server must support such an entry. Not all dns providers support CAA entries. 4. Content- and Performance-critical Checks A Good: All checks /.well-known/acme-challenge/random-filename without redirects answer with the expected http status 404 - Not Found. Creating a Letsencrypt certificate via http-01 challenge should work. If it doesn't work: Check your vHost configuration (apachectl -S, httpd -S, nginx -T). Every combination of port and ServerName / ServerAlias (Apache) or Server (Nginx) must be unique. Merge duplicated entries in one vHost. If you use an IIS, extensionless files must be allowed in the /.well-known/acme-challenge subdirectory. Create a web.config in that directory. Content: <configuration><system.webServer><staticContent><mimeMap fileExtension="." mimeType="text/plain" /></staticContent></system.webServer></configuration>. If you have a redirect http ⇒ https, that's ok, Letsencrypt follows such redirects to port 80 / 443 (same or other server). There must be a certificate. But the certificate may be expired, self signed or with a not matching domain name. Checking the validation file Letsencrypt ignores such certificate errors. Trouble creating a certificate? Use https://community.letsencrypt.org/ to ask. A Info: No img element found, no alt attribute checked 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: 318763 milliseconds, 318.763 seconds