How is substack.com?

Looks fine risk 0/100

Registered 16 years ago, on no blocklists we checked, valid HTTPS, the site answered 200 in 638 ms.

Why

02050100

finecarefulhigh risk

·Nothing in the checks added risk.

Rule-based: domain age, blocklists, TLS. A heuristic, not a guarantee.

The home page, rendered by how.is in a sandboxed browser. Nothing on it is clickable here.

Site

200

638 ms

HTTPS

52 d

left on a Google Trust Services certificate

Age

16 years

registered 2010-04-27

Blocklists

listings across 5 lists

Everything we looked at

DNS records5 record types

A	104.18.37.200 172.64.150.56
AAAA	2606:4700:4401::ac40:9638 2606:4700:4404::6812:25c8
MX	10 mxa.mailgun.org 10 mxb.mailgun.org
NS	ali.ns.cloudflare.com lee.ns.cloudflare.com
TXT	google-site-verification=SXEl7_p4SBszcanSWwVc_3-RFky80c0-94janbeeWI4 google-site-verification=DAkdykID6WqQM6tT7IfSu9_uB7-qIdB039MA_C3T3eA tiktok-developers-site-verification=A9XRSo8lWy5CPFJ0bqI04KCpUZGAAq7p google-site-verification=vQEKLOUDfKNOQAv9W3EUMiRD6e5ibAEPhc2yCzP7big tiktok-developers-site-verification=7PgqCAJ52ILLOqf2KELd8uaRfJpuzaLQ google-site-verification=FfNIQIxsRHpj3Y7E_d3N6GFqGgWDZ-sfYojqCilwtqE v=spf1 include:_spf.google.com include:mailgun.org include:mail.zendesk.com ~all facebook-domain-verification=8vbxp2ntmkudc6is3h5r840c9fwo7f google-site-verification=4V_X38Yf0J4VJcWFwtG38bOS1nkOWeIWJhticlMgNQE

RegistrationAmazon Registrar, Inc.

registrar	Amazon Registrar, Inc.
registered	2010-04-27
expires	2030-04-27
last changed	2026-05-16
owner	c/o whoisproxy.com
nameservers	ali.ns.cloudflare.com lee.ns.cloudflare.com
status	client transfer prohibited

registered 2010-04-27expires 2030-04-27

HTTPS certificate52 days left

valid	yes
issuer	Google Trust Services
covers	substack.com, *.substack.com
protocol	TLSv1.3

issued 2026-09-19expires 2026-12-18

DNSSECinsecure

Domain is not signed with DNSSEC

. → com → substack.com

Email authenticationexcellent

SPF	pass `v=spf1 include:_spf.google.com include:mailgun.org include:mail.zendesk.com ~all`
DMARC	pass policy reject
DKIM	found: google

Whether mail claiming to be from this domain can be checked as genuine.

Security scoregrade B · 160/205

Basic Security

10/40missing: DNSSEC Enabled, Nameserver Diversity

Record Security

30/45missing: CAA Records, DKIM Presence

Advanced Security

25/25

Domain Reputation

50/50

Threat Detection

45/45missing: Domain Age Check

Blocklists0 listings · 8 lookups

SURBL MultidomainURIBL MultidomainSpamCop104.18.37.200Barracuda104.18.37.200UCEPROTECT Level 1104.18.37.200SpamCop172.64.150.56Barracuda172.64.150.56UCEPROTECT Level 1172.64.150.56

Green: clean. Red: listed. Grey: the list did not answer.

Ask it yourself

Agents get this as data. Bought through the API, the checks behind this page cost $0.070: profile $0.025 + trust $0.020 + screenshot $0.020 + site status $0.005.

curl "https://how.is/v1/domain/trust?domain=substack.com" \ -H "Authorization: Bearer $HOWIS_KEY" # or pay per call in USDC (x402), no key: the 402 tells your agent the price curl -i "https://how.is/v1/domain/profile?domain=substack.com"

MCP: add https://how.is/mcp to Claude, Codex or Cursor (one-line install) and ask for domain_trust on substack.com. Reference: /llms.txt.

Watch substack.com. DNS read at the source every 5 minutes; certificate, blocklists and expiry every 6 hours. You get an email only when something changes.

Watch — $1 / 30 days