Last update: 2026-01-27
The Null MX Record
When a mail client attemps to send email to your domain, it will first lookup MX records and will fallback to the A/AAAA record if no MX is found.
Now, let's say you have a domain name that doesn't send nor receive any email, If you just don't set any MX records, mail clients may still attempt email delivery if you have A/AAAA records.
That's where the Null MX record (aka "No Service MX RR") comes in. It allows you to indicate that no mail servers are available for your domain. The Null MX record looks like this:
yourdomain.example. MX 0 .
It's basically a MX DNS record with a priority of 0 and a value of ..