What Does an MX Record Actually Do? A Beginner’s Guide

An MX (Mail Exchange) record is a line in a domain's DNS settings that answers one specific question: which mail server should receive email sent to this domain? Without at least one correctly configured MX record, a domain simply cannot receive mail - every message sent to it bounces, no matter how correctly everything else is set up.

How priority actually works

A domain can publish more than one MX record, each with a priority number. Lower numbers are tried first; a receiving mail transfer agent always attempts the lowest-numbered server before falling back to a higher-numbered one. This is not a load-balancing mechanism by default - it is a primary-then-backup order, so a second MX record with a higher number exists purely as a fallback if the first one is unreachable.

What it looks like when something is wrong

A domain with no MX record at all cannot receive any mail - messages bounce immediately with an error referencing the domain, not the specific address. A domain with an MX record pointing at a server that no longer exists (common after a provider migration that missed updating DNS) behaves the same way from the sender's side: a bounce, sometimes delayed by hours while retries are attempted.

When this is worth checking

• Right after registering a new domain and pointing it at a mail provider, to confirm the setup actually propagated.
• After migrating between providers (e.g. moving to Google Workspace or Microsoft 365), since a missed MX update is one of the most common migration mistakes.
• Before adding an unfamiliar domain to an important list - a domain with no MX record at all is an immediate, unambiguous red flag.

Frequently Asked Questions

Can a domain have both a website and email working with the same DNS setup?

Yes - the A/CNAME records that point a domain at a website and the MX records that route its mail are entirely separate entries and do not conflict. A domain can point its website to one host and its mail to a completely different provider without any issue.

How long does it take for a new or changed MX record to start working?

DNS propagation for MX records is usually fast - often under an hour - but can take up to 24-48 hours in rare cases depending on the previous record's TTL setting and how quickly resolvers around the world refresh their cache.