The simple explanation
Think of MX records like a postal forwarding address. When someone sends an email toyou@yourcompany.com, their mail server looks up the MX record foryourcompany.com to find out which server should receive it. Without an MX record, email sent to your domain has nowhere to go and bounces back.
What an MX record looks like
A domain can have multiple MX records, each with a priority number:
yourcompany.com MX 10 aspmx.l.google.com yourcompany.com MX 20 alt1.aspmx.l.google.com yourcompany.com MX 30 alt2.aspmx.l.google.comThe priority number (10, 20, 30) tells sending servers which to try first. Lower number = higher priority. If the primary server is unavailable, the sending server tries the next one in order. This is how email stays reliable even when one server is down.
Common MX record setups
Your MX records depend on where you receive email:
- Google Workspace:
aspmx.l.google.com(and several alt servers) - Microsoft 365:
yourcompany-com.mail.protection.outlook.com - Zoho Mail:
mx.zoho.com - Self-hosted: your own mail server's hostname
What breaks when MX records are wrong
MX record problems are usually one of three things:
No MX records at all
Incoming email bounces immediately. The sender gets a "550 No such user" or similar error. This happens after domain migrations when someone forgets to set up MX on the new registrar.
MX records pointing to the wrong server
Email is delivered to a server that isn't expecting it and disappears. This is common when you switch email providers and update some records but not others.
MX records pointing to an IP address
MX records must point to a hostname, not an IP address directly. Pointing an MX record to an IP is a configuration error — many mail servers will refuse to deliver to it.
MX records vs A records
People sometimes confuse MX records with A records. An A record points your domain to an IP address (for websites). An MX record points to a mail server hostname (which itself has an A record). They serve completely different purposes — changing your website's A record has no effect on email, and vice versa.
How to check your MX records
You can look up your MX records with the dig command:
dig MX yourdomain.comOr use EmailHealth's free MX lookup tool above to check them instantly.