MX host has no reverse DNS (PTR) record
One or more of `your domain`'s MX hosts publish no PTR record for any of its addresses.
Why it matters
One or more of `your domain`'s MX hosts publish no PTR record for any of its addresses. A receiving IP with no reverse DNS is a signal several spam filters weight against a connection, which can affect whether DMARC aggregate reports and replies to your transactional email actually reach you. Managed providers (Google Workspace, Microsoft 365, and similar) always publish this correctly — this usually means a self-hosted mail server whose IP's reverse zone was never delegated to it by the hosting provider.
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.
One or more of your domain's MX hosts have no PTR (reverse DNS) record for any of their addresses: your mail servers. Several spam filters weight a receiving IP with no reverse DNS against it, which can affect whether DMARC aggregate reports and replies to your transactional email actually reach you. If these are self-hosted mail servers, ask whoever controls the IP allocation (your hosting/cloud provider, or your IP's ISP if you own the block) to set a PTR record for each address pointing back at its MX hostname. If these hosts belong to a managed provider (Google Workspace, Microsoft 365, etc.), this usually means a stale or misconfigured MX record pointing at an IP outside that provider's normal range — verify the MX hostnames against your provider's current setup instructions.
Frequently asked questions
- What does "MX host has no reverse DNS (PTR) record" mean?
- One or more of `your domain`'s MX hosts publish no PTR record for any of its addresses.
- How serious is it?
- ShipReady rates this low. Worth fixing. Small individually, and they accumulate.
- 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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