Null MX record: how to say a domain takes no email
A null MX record (MX 0 ".") tells mail servers a domain accepts no email. What it does, how to add it at Cloudflare and others, and what to pair it with.
Updated 20 Oct 2026. About 1 minute to read.
A null MX record is an MX record with priority 0 and a single dot as the mail server: yourdomain.com. MX 0 .. RFC 7505 defines it to mean "this domain accepts no email". Senders that see it fail at once instead of retrying for days, and bounces from spam sent in your name have nowhere to go.
When to use it
On any domain that should never receive mail: parked names, redirect-only domains, old brands. Do not add it to a domain with mailboxes on it. It replaces the existing MX records, and mail to those mailboxes would stop.
Pair it with SPF and DMARC
A null MX only speaks about receiving. It does nothing to stop someone sending fake mail as the domain. For that, a no-mail domain needs two more records:
| Type | Name | Value |
|---|---|---|
| MX | @ | . with priority 0 |
| TXT | @ | v=spf1 -all |
| TXT | _dmarc | v=DMARC1; p=reject; |
With all three, Warnwell's email lamp reads "Locked down: takes no mail, fakes rejected". With SPF and DMARC but no null MX, it says the domain "Can be locked down further".
Adding it
- Cloudflare: Add record, type MX, name @, mail server
., priority 0. Cloudflare accepts the dot. - Some DNS hosts refuse "." as a mail server. If yours does, leave the MX out and keep the SPF and DMARC records. They do the important part.
Delete any other MX records on the domain first. A null MX next to a real one confuses senders and checkers alike.