MX Lookup

About MX Record Lookup

Mail Exchanger (MX) records are DNS entries that specify which mail servers are authorised to accept incoming email on behalf of a domain. When someone sends an email to user@example.com, the sender's mail server queries DNS for the MX records of example.com to discover where to deliver the message.

Understanding MX records

Each MX record has two components:

• Priority (preference number) — A lower number means higher priority. Sending mail servers always try the highest-priority (lowest number) server first. If it is unavailable, they fall back to lower-priority alternatives.
• Hostname — The fully qualified domain name of the mail server (e.g. mail.example.com, aspmx.l.google.com for Google Workspace, or mail.protection.outlook.com for Microsoft 365).

Common MX configurations

• Google Workspace — Multiple aspmx.l.google.com and alt*.aspmx.l.google.com entries with priorities 1, 5, and 10.
• Microsoft 365 — A single entry ending in .mail.protection.outlook.com with priority 0.
• Self-hosted — Your own mail server hostname, often with a backup at a higher priority number (e.g. priority 10 for the backup).

Common use cases for checking MX records

• Verifying that email for a domain routes to the correct provider after migration
• Troubleshooting email delivery failures or bounces
• Confirming MX records have propagated following a DNS change
• Checking whether a backup MX server is properly configured

For a complete email health check, use the MX Health Summary tool, which also checks SPF, DMARC, DKIM, and blacklist status in a single view.