Only one mail server host is published
Updated
38% of the 852 domains we could check get a warning for this. Sample: the first 1,000 domains by rank in the Majestic Million, checked on 2026-10-12. How we measured
What this check looks for
All of your inbound mail depends on a single server. If it is unreachable, senders queue messages and eventually give up, and some mail is lost.
Why it matters
Senders typically retry for a few days, so a short outage is survivable — but a longer one, or a sender with a short retry window, means messages bounce.
When the check passes, your report says: “More than one mail server host is published”.
What it costs your score
When this check fails it removes 8 points from your Email transport score, before the status, confidence and repeat multipliers are applied. Email transport carries a weight of 8 in the overall score.
It shares the email-transport.mx family ceiling of 30 points: however many findings that family produces, together they cannot remove more than that from Email transport. One underlying problem showing up in several places is still one problem.
- Severity
- medium
- Default confidence
- high
- Status when triggered
- warn
- Deduction
- 8 points
- Family cap
- email-transport.mx · 30
- Category
- Email transport
- Module
- Email mx
- Fix owned by
- dns host
- In the ruleset since
- 2026.09
How to fix it
Publish at least one backup MX, or confirm your provider's single name is multi-homed.
One host means one point of failure for everything sent to you.
If you use a hosted provider, check their documentation — many publish several MX names and you may have entered only one.
If you run your own mail server, add a second host at a higher preference number, on separate infrastructure.
A backup MX must be configured to relay to the primary and to apply the same anti-spam checks, or it becomes a way around them.
How to confirm it worked
dig +short MX ‹domain› — expect two or more targets
A named slot like ‹domain› — and the braces left in the configuration below — is filled in with your own values when this rule appears on a report.
Technical detail
‹domain› publishes ‹mx targets›, resolving to ‹mx addresses›. RFC 5321 §5.1 describes trying MX hosts in preference order; with a single host there is nothing to fall back to. Note that a hosted provider often publishes one name that resolves to many addresses across regions, which is genuine redundancy — this finding is downgraded when we can confirm that.
Standards and references
Test this on your domain
Run the check that produces this finding, on its own, against any domain.