MTA-STS policy file is malformed
`your domain` publishes an MTA-STS TXT record, so it has declared intent to use MTA-STS, but the policy file at the published policy URL does not parse as a valid policy: the value.
Why it matters
`your domain` publishes an MTA-STS TXT record, so it has declared intent to use MTA-STS, but the policy file at the published policy URL does not parse as a valid policy: the value. Senders that support MTA-STS cannot apply any protection from a policy they cannot parse, so this domain currently gets none of the benefit despite looking configured.
How ShipReady detects it
Email-authentication DNS records (DMARC / SPF). Almost every AI-built SaaS sends transactional email — password resets, magic links, receipts — through Resend, SendGrid or Postmark. Setting that up gets the mail delivered; it does not stop anyone else sending mail that claims to come from the same domain. Without a DMARC policy, a receiving server has no instruction to reject a forgery, so an attacker can send "reset your password" from the product's own domain and the message will land in the inbox looking authentic. This check is almost entirely DNS rather than HTTP — one exception is MTA-STS, whose policy is only half-published in DNS; the other half is a file fetched over HTTPS (see _check_mta_sts). Nearly everything else here is the most deterministic kind of check the scanner has: a record either exists or it does not, so there is no heuristic and no false-positive surface. The one place judgement is required is deciding WHICH domain to ask about — see _organizational_domain.
Detection is deterministic. ShipReady reports this only when it observes the condition directly, and prefers to miss a real problem over inventing one. Rule version 1.10.0.
How to fix it
This is the prompt ShipReady puts in your report — written to be pasted straight into Cursor, Claude Code, or whichever assistant built the app.
your domain's MTA-STS policy file at the published policy URL does not parse as valid: one or more format errors. Senders that support MTA-STS cannot apply any protection from a policy body they cannot parse. Rewrite the file to the exact RFC 8461 format: one "key: value" pair per line, with "version: STSv1", a "mode:" of none/testing/enforce, at least one "mx:" line naming an MX hostname from your MX record, and a "max_age:" between 1 and 31557600 (seconds).
Frequently asked questions
- What does "MTA-STS policy file is malformed" mean?
- `your domain` publishes an MTA-STS TXT record, so it has declared intent to use MTA-STS, but the policy file at the published policy URL does not parse as a valid policy: the value.
- How serious is it?
- ShipReady rates this medium. Fix soon. Meaningfully weakens a defence or degrades how the site works.
- How do I fix it?
- Paste the fix prompt on this page into Cursor, Claude Code or your AI editor. It is the same prompt ShipReady puts in your report.
- Can I check my own site?
- Yes — ShipReady scans up to ten pages of any public site for free and reports this alongside every other check. The free report lists every issue it finds and shows full evidence and a fix prompt for the critical and high-severity ones; medium and low findings are counted and unlock on Pro.
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