What is MX Record?

An MX (Mail Exchange) record is a DNS entry that tells the rest of the internet which mail server is responsible for receiving email for your domain. Without one, mail sent to your domain has nowhere to go.

How MX records work

You publish one or more MX records pointing at mail servers, each with a priority (lower = preferred):

yourdomain.com.   MX   10   inbound-smtp.us-east-1.amazonaws.com.
yourdomain.com.   MX   20   backup-mail.yourdomain.com.

When someone emails you@yourdomain.com, their server looks up your MX records and delivers to the highest-priority server that answers, then falls back to the next on failure.

Why it matters

MX records are what make a domain able to receive mail at all. A disposable-inbox service like Devmailr owns a domain and points its MX records at its own receiving infrastructure, which is why any prefix@devmailr.app address can accept mail. Closely related is the catch-all setup, which accepts mail for every address at a domain.