substack.com DMARC Checker

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DMARC Check for substack.com

The DMARC record for substack.com is published as a DNS TXT record at _dmarc.substack.com. It tells receiving mail servers what to do when an email claiming to be from substack.com fails SPF and DKIM authentication checks: whether to deliver it normally, send it to spam, or reject it entirely.

DMARC also provides substack.com's administrators with visibility into who is sending email using their domain. Through aggregate reports (rua) and forensic reports (ruf), domain owners can monitor authorized and unauthorized email activity.

This DMARC checker shows substack.com's current DMARC policy, alignment settings, and reporting configuration. A well-configured DMARC policy is essential for protecting substack.com from email spoofing and phishing attacks.

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What Is DMARC?

DMARC is an email authentication policy layer that sits on top of SPF and DKIM. While SPF verifies the sending server and DKIM verifies the message hasn't been altered, DMARC ties them together by requiring that at least one of these checks "aligns" with the From header domain.

Without DMARC, even if substack.com has SPF and DKIM configured, receiving servers have no instruction on what to do when authentication fails. DMARC fills this gap by providing an explicit policy (none, quarantine, or reject) and a feedback mechanism through reporting.

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DMARC Policies Explained

DMARC has three policy levels. "p=none" is monitor-only mode, authentication failures are reported but email is delivered normally. This is the recommended starting point for substack.com when first implementing DMARC. "p=quarantine" sends failing emails to the spam/junk folder. "p=reject" blocks them entirely, providing the strongest protection.

The "pct" tag controls what percentage of failing messages the policy applies to, allowing a gradual rollout. For example, substack.com could start with "p=reject; pct=10" to reject only 10% of failing messages while monitoring the impact, then gradually increase to 100%.

Most organizations roll out DMARC in phases: start with "p=none" to gather data, analyze reports to identify all legitimate email sources, add them to SPF/DKIM, then move to "p=quarantine" and finally "p=reject". substack.com's current policy level reveals where it sits in this rollout.

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DMARC Alignment

DMARC requires that either SPF or DKIM "aligns" with the From header domain. For substack.com, this means the SPF-authenticated domain or the DKIM signing domain must match substack.com (or a subdomain of substack.com in relaxed mode).

Alignment can be "strict" (exact domain match only) or "relaxed" (organizational domain match, allowing subdomains). The "aspf" tag controls SPF alignment and "adkim" controls DKIM alignment. Most domains use relaxed alignment (the default) because it's more flexible while still providing good protection.

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Frequently Asked Questions

Does substack.com have DMARC?. The DMARC analysis for substack.com shows whether the domain has a published DMARC record at _dmarc.substack.com. If no record is found, substack.com has not configured a DMARC policy.

What is substack.com's DMARC policy?. The policy level (none, quarantine, or reject) is reported in the DMARC analysis. "reject" provides the strongest protection, while "none" is monitoring-only.

Does substack.com enforce email authentication?, A DMARC policy of "quarantine" or "reject" indicates that substack.com actively enforces email authentication. A policy of "none" means substack.com monitors but doesn't enforce.

How do I set up DMARC for my domain?, Start by creating a TXT record at _dmarc.yourdomain.com with the value "v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com". Monitor the reports, then gradually increase enforcement to quarantine and reject.