MX record points to a hostname with no address
One or more of `your domain`'s MX hosts resolve to no A or AAAA record, so a sending server has a hostname from the MX lookup but no IP address to actually connect to.
3% · n=32 · as of 15 September 2026 of sites ShipReady scanned had this, counted across sites where this check completed.
Why it matters
One or more of `your domain`'s MX hosts resolve to no A or AAAA record, so a sending server has a hostname from the MX lookup but no IP address to actually connect to. Mail addressed to this domain bounces at the affected hosts — the usual cause is a mail server that was decommissioned, or a DNS record left pointing at an old provider after switching.
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.
The MX record for your domain points at one or more hostnames with no A or AAAA record: your mail servers. A sending server gets these hostnames back from the MX lookup but has no IP address to connect to, so mail bounces. This usually means the mail server was decommissioned or the DNS record was never updated after switching providers. Check your email provider's current setup instructions for the correct MX hostnames, update the MX record to point at them, and remove any MX entry for a hostname you no longer control.
Frequently asked questions
- What does "MX record points to a hostname with no address" mean?
- One or more of `your domain`'s MX hosts resolve to no A or AAAA record, so a sending server has a hostname from the MX lookup but no IP address to actually connect to.
- How serious is it?
- ShipReady rates this high. Fix before launch. A real weakness that an attacker can act on.
- How common is this?
- Across the sites ShipReady has scanned where this check completed, 3% · n=32 · as of 15 September 2026.
- 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.
Related checks
Run this check on your site
ShipReady checks this and 193 other things across up to ten pages of your site, with an AI-ready fix for each. Free, no signup.