Fixing "MX record refers to a host with no address record"

Sending servers report variants of this when they try to deliver to you:

example.com: MX record refers to a host (mail.exmaple.com)
  that has no A/AAAA record — cannot deliver

MX records must point at a hostname that itself resolves to an IP. If that hostname has no A/AAAA record, there is nowhere to connect, and mail either bounces or queues until it times out.

Why it happens

Typically a typo in the MX target (exmaple.com), an MX pointing at a host that was decommissioned, a CNAME used as an MX target (forbidden by RFC 2181), or a trailing-dot mistake that turned an absolute name into a relative one.

Diagnose it

Run the MX check below: it resolves every MX target to its IPs and flags any that don't resolve, plus duplicate or0 . "null MX" records. An MX row with no IP is the broken one.

Fix it

1. Correct the MX target to a hostname that has a published A/AAAA record.

2. Never point an MX at a CNAME — use the real hostname.

3. If you don't accept mail at all, publish a proper null MX: 0 .

4. Re-check propagation; stale caches can serve the old broken target for the TTL window.