MX Record Lookup

MX records are the DNS entries that tell the internet where to deliver email for your domain. If someone sends a message to you@yourdomain.com, their mail server queries DNS for your MX records, gets back a list of mail servers with priorities, and delivers to the highest-priority one that responds. Get this wrong and your domain simply can't receive email — messages bounce back to the sender with a "host not found" error.

How MX record priority works

Each MX record has two parts: a priority number and a mail server hostname. Lower priority numbers mean higher preference. If you have MX records with priorities 10, 20, and 30, mail servers try priority 10 first. If that server is down, they try 20, then 30. Most email providers give you multiple MX records for redundancy. Google Workspace, for example, uses five: aspmx.l.google.com (priority 1), alt1.aspmx.l.google.com (priority 5), and three more at priorities 10, 10, and 10.

What MX records tell you about a domain

MX records are public, so you can look up any domain's email provider. aspmx.l.google.com means Google Workspace. mail.protection.outlook.com means Microsoft 365. mx1.emailsrvr.com means Rackspace. This is useful for sales teams researching prospects, for deliverability debugging, and for verifying that a domain is set up to receive email before you send to it. Our email validator uses MX lookups as part of its verification process.

Common MX configuration problems

The most frequent mistake is pointing MX records to an IP address instead of a hostname — MX records must use hostnames. Another common issue: setting all MX records to the same priority, which causes random distribution instead of proper failover. If you've recently switched email providers (say, from Microsoft 365 to Google Workspace), stale MX records pointing to the old provider will cause messages to disappear silently. Always verify with our DNS propagation checker after making changes.

MX records and email authentication

MX records handle inbound mail, but they're closely related to your outbound authentication setup. The mail servers in your MX records should also be authorized in your SPF record if they send outgoing email (like auto-replies or forwarding). Make sure your entire email infrastructure — MX, SPF, DKIM, and DMARC — is consistent. If you're troubleshooting delivery issues, run a WHOIS lookup to check the domain's registration status and a blacklist check on your mail server IPs.