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Total

DNS

Email

Security

Network

100

Availability

Domainsubstack.com

IPv42

IPv62

MX records2

StatusActive

Domain technical report

Substack

substack.com

The app for independent voices

Generated: 2026-08-08T17:24:44-05:00 · Cached result

JSON CSV PDF Visit site

IPv42

IPv62

MX2

NS2

DiagnosticsMain findings and recommendations

✓

IPv4 (A)30 / 30 pts · Dns

2 IPv4 address(es) detected.

✓

IPv6 (AAAA)10 / 10 pts · Dns

2 IPv6 address(es) detected.

✓

Name server redundancy20 / 20 pts · Dns

2 NS record(s); 2 or more required.

✓

SOA record10 / 10 pts · Dns

Authoritative zone record.

DNSSEC chain0 / 15 pts · Dns

Both DS and DNSKEY are required.

CAA policy0 / 5 pts · Dns

Certificate authority restriction.

✓

DNS propagation10 / 10 pts · Dns

Agreement between public resolvers.

✓

MX records20 / 20 pts · Mail

2 MX record(s).

✓

SPF25 / 25 pts · Mail

SPF policy published.

✓

DMARC25 / 25 pts · Mail

DMARC policy published.

✓

DKIM20 / 20 pts · Mail

A DKIM selector was verified.

MTA-STS0 / 5 pts · Mail

Mail transport policy.

TLS-RPT0 / 5 pts · Mail

TLS reporting policy.

✓

Valid TLS certificate55 / 55 pts · Security

72 day(s) remaining.

✓

Certificate lifetime10 / 10 pts · Security

Full points require at least 30 days remaining.

HTTP security headers8 / 35 pts · Security

2 of 9 evaluated headers detected.

PTR reverse DNS0 / 30 pts · Network

PTR not detected.

✓

IPv4 diversity35 / 35 pts · Network

Two or more IPv4 addresses receive full points.

✓

IPv6 connectivity35 / 35 pts · Network

AAAA availability.

✓

DNS resolution40 / 40 pts · Availability

At least one address family must resolve.

✓

HTTP response40 / 40 pts · Availability

HTTP/2 200

✓

HTTPS final URL20 / 20 pts · Availability

Final URL uses HTTPS.

DNS and emailPublished records and email configuration

A

2 record(s)

172.64.150.56
104.18.37.200

AAAA

2 record(s)

2606:4700:4401::ac40:9638
2606:4700:4404::6812:25c8

CNAME

0 record(s)

—

Not configured

MX

2 record(s)

10 mxb.mailgun.org.
10 mxa.mailgun.org.

TXT

9 record(s)

"google-site-verification=DAkdykID6WqQM6tT7IfSu9_uB7-qIdB039MA_C3T3eA"
"facebook-domain-verification=8vbxp2ntmkudc6is3h5r840c9fwo7f"
"google-site-verification=FfNIQIxsRHpj3Y7E_d3N6GFqGgWDZ-sfYojqCilwtqE"
"v=spf1 include:_spf.google.com include:mailgun.org include:mail.zendesk.com ~all"
"google-site-verification=4V_X38Yf0J4VJcWFwtG38bOS1nkOWeIWJhticlMgNQE"
"tiktok-developers-site-verification=A9XRSo8lWy5CPFJ0bqI04KCpUZGAAq7p"
"google-site-verification=SXEl7_p4SBszcanSWwVc_3-RFky80c0-94janbeeWI4"
"google-site-verification=vQEKLOUDfKNOQAv9W3EUMiRD6e5ibAEPhc2yCzP7big"
"tiktok-developers-site-verification=7PgqCAJ52ILLOqf2KELd8uaRfJpuzaLQ"

NS

2 record(s)

lee.ns.cloudflare.com.
ali.ns.cloudflare.com.

SOA

1 record(s)

ali.ns.cloudflare.com. dns.cloudflare.com. 2410510401 10000 2400 604800 1800

SPF

Configured

v=spf1 include:_spf.google.com include:mailgun.org include:mail.zendesk.com ~all

DMARC

Configured

v=DMARC1; p=reject; pct=100; rua=mailto:re+kvnosxqvppz@dmarc.postmarkapp.com; sp=reject; aspf=r;

DKIM

Selector google

v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAhSxZK3Q0YieBvcdcHojJLJQK1ooDVYtpjy3A7lEj/q6lDKTSAazT0jUd+AEUShEYBndvQ+RNwRJ1NEUtg686FGK9Vs7uX7iwGC+CuCuL4BvQ8W0ktGddMZv4mWs9ycrEpLFFBnixvN1kEXaQuyAb3o2hR SFYBkiybC5uCYggpL2nG/HTNHg5fMxMCH2HeaGm ACgWJDMPJIzko08rb30cWoOxYpZKqmfnzECnRxA2R8rr03sdWhGQ7b72AeuZ9MexplWTWD6qGYevMugV/fnVpb91Jb0b2rpS2G3PXCtt 2GQsFStzDhXN+6K6NdOjdGNcYOxcVF3Tamyc4A5c9AVgsQIDAQAB

Analyzed webpageMetadata and HTTP response

Title and description

Extracted

Title

Substack

Description

The app for independent voices

Final URL

https://substack.com/

HTTP status

200

HTTP

Status

HTTP/2 200

Final URL

https://substack.com/

Version

Server

cloudflare

X-Powered-By

Express

SSL and HTTP securityCertificate, protocol and security headers

SSL certificate

Available

Yes

Issuer

Google Trust Services

substack.com

Valid from

2026-07-22T04:54:58-05:00

Valid until

2026-10-20T05:54:53-05:00

Days remaining

Protocol

TLSv1.3

Cipher

TLS_AES_256_GCM_SHA384

Security headers

2 active

✓

HSTSImplemented

✓

Content Security PolicyImplemented

—

X-Content-Type-OptionsNot detected

—

X-Frame-OptionsNot detected

—

Referrer PolicyNot detected

—

Permissions PolicyNot detected

—

Cross-Origin-Opener-PolicyNot detected

—

Cross-Origin-Embedder-PolicyNot detected

—

Cross-Origin-Resource-PolicyNot detected

DNS propagationComparison across public resolvers

Public resolver comparison

Consistent

✓

Consistent propagation

5 public resolvers queried.

ResolverServerResultLatency

Google

8.8.8.8

104.18.37.200, 172.64.150.56

53,01 ms

Cloudflare

1.1.1.1

104.18.37.200, 172.64.150.56

39,24 ms

Quad9

9.9.9.9

104.18.37.200, 172.64.150.56

23,94 ms

OpenDNS

208.67.222.222

104.18.37.200, 172.64.150.56

31,99 ms

AdGuard

94.140.14.14

104.18.37.200, 172.64.150.56

64,12 ms

IP, geolocation and ASNAssociated network information

172.64.150.56

No data

success

country

region

city

asn

organization

isp

104.18.37.200

No data

success

country

region

city

asn

organization

isp

Visitor information

Visitor

216.73.217.62

reverse

country

country_code

region

city

latitude

longitude

isp

organization

asn

timezone

browser

Other

language

user_agent

Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)

is_bot

Yes

cloudflare

SMTPEmail port connectivity

mxb.mailgun.org

Port 25: Closed/unreachable - 9 ms - 
Port 465: Closed/unreachable - 4028.3 ms - 
Port 587: Closed/unreachable - 4021 ms -

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