Definition
An MX server is the destination for incoming email addressed to a domain, identified by an MX record in DNS. It includes a priority for failover.
A missing or incorrect MX record causes mail to bounce or queue.
The MX server is the gatekeeper for all incoming mail, so a misconfigured record stops delivery entirely. Redundant records with priorities keep mail flowing through failures. Verifying after DNS changes prevents silent outages.
How MX Records Work
Senders look up the MX record to find where to deliver.
Multiple records with priorities provide failover.
Why It Matters
The MX server is the gatekeeper for all incoming mail, so a misconfigured record stops delivery entirely. For any business that receives replies, correct MX configuration is a non-negotiable foundation.
Best Practices
- Keep MX records accurate and redundant.
- Check MX records when changing mail providers.
- Use MX lookup tools to verify the destination.
- Keep MX records accurate and update them when you change mail providers.
- Use at least two MX records with different priorities for redundancy.
- Verify MX records after any DNS migration.
- Check that the MX hostname resolves to a valid IP.
- Monitor receiving-side queues.
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Frequently Asked Questions
A DNS record that names the mail server responsible for receiving email for a domain. The MX server is the gatekeeper for all incoming mail, so a misconfigured record stops delivery entirely.
Incoming mail will be rejected, bounce, or queue at the sender. Redundant records with priorities keep mail flowing through failures.
Yes, with different priorities for failover. Verifying after DNS changes prevents silent outages.
Use a DNS lookup tool or the dig command. The MX server is the gatekeeper for all incoming mail, so a misconfigured record stops delivery entirely.
No, but you need them to receive replies. Redundant records with priorities keep mail flowing through failures.