HighInfrastructure · usually high
An MX host does not resolve to an address
A mail exchanger is published but its hostname has no A or AAAA record.
Check your own domain
What causes this
A sending server looks up your MX records, then resolves each hostname to an IP address to connect to. If the hostname does not resolve, that mail exchanger cannot be reached at all. Where it is the only or highest-priority exchanger, delivery to your domain fails.
What it breaks
Mail delivery to your domain fails or is delayed while senders retry an unreachable host.
How to fix it
Correct the hostname or remove the record.
- Check the MX hostname for typos against your provider's documentation.
- Confirm the hostname resolves. If the host has been decommissioned, remove the MX record.
Related problems
- No email configuration of any kind was foundNo MX, SPF or DMARC records exist for this domain.
- MTA-STS is not configuredThe domain does not publish an MTA-STS policy. This is optional but worth having.
- MTA-STS record published but the policy file is unreachableThe DNS record announces a policy that cannot be fetched.
- An MX record points at an aliasMX targets must be hostnames with address records, not CNAMEs.
- No MX records foundThis domain publishes no mail exchangers, so it cannot receive email.