MX Lookup

MX Record Lookup

What Are MX Records and How Does Email Routing Work?

An MX record, short for Mail Exchanger record, is a type of DNS entry that tells the internet which mail servers are responsible for accepting email on behalf of a domain. When someone sends an email to an address like user@example.com, their mail server first performs a DNS lookup to find the MX records for example.com. Those records point to one or more mail server hostnames — such as mail.example.com or aspmx.l.google.com — and the sending server then connects to that destination to deliver the message.

Without MX records, a domain cannot receive email at all. Even if a website is live and fully functional, email delivery will fail silently if MX records are missing or misconfigured. MX records are entirely separate from the A or CNAME records that control web traffic, which is why a domain can host a website on one server while routing all its email through a completely different provider — for example, running a website on a web host while using Google Workspace or Microsoft 365 to handle email.

How to Read MX Priority Values

Every MX record includes a priority number (sometimes called preference value). This number controls the order in which mail servers are tried. A lower number means higher priority — the sending server will always attempt delivery to the lowest-numbered host first. If that server is unreachable or returns an error, the next-lowest priority server is tried, and so on down the list.

For example, a domain with two MX records might have:

• Priority 10 — mail.example.com (primary, tried first)
• Priority 20 — backup-mail.example.com (fallback, used only if priority 10 fails)

When two records share the same priority value, the sending mail server picks between them randomly, which distributes load across multiple servers. Google Workspace, for instance, uses this pattern across its five MX hosts to balance incoming email traffic. If this tool returns results sorted by ascending priority, the first row is always the mail server that senders will contact under normal conditions.

Common Use Cases for an MX Lookup

Troubleshooting email delivery problems is the most frequent reason to run an MX lookup. If people are reporting that email sent to your domain is bouncing or being rejected, the first thing to verify is whether your MX records exist and point to the correct mail server. A missing record, a typo in the hostname, or a record still pointing at an old provider are all common culprits. Pairing an MX lookup with the Email Auth Checker lets you verify both routing and authentication (SPF, DKIM, DMARC) in one diagnostic session.

Verifying mail server setup is equally important when you are configuring a new email service for the first time. After you add MX records at your domain registrar or DNS host, it can take anywhere from a few minutes to 48 hours for those records to propagate globally. Running a lookup here confirms the records are live and correctly formatted before you start testing email flow. You can cross-reference the mail server hostname against what your email provider told you to expect.

Checking after a domain migration is critical any time you move a domain to a new registrar, switch DNS providers, or change email platforms. During a migration, MX records are among the most important records to verify because even a brief misconfiguration can cause incoming email to bounce or be silently dropped. For a complete post-migration audit, combine this tool with a full DNS Record Lookup to confirm A, NS, and TXT records have also transferred correctly. If you have recently moved a domain and want to verify the old PTR record is gone, the Reverse DNS Lookup can help confirm hostname resolution is consistent with your new setup.

Related Tools & Resources

For a full view of a domain’s DNS configuration, use the DNS Record Lookup. To verify that email authentication is properly configured — including SPF, DKIM, and DMARC policies — use the Email Auth Checker. To build SPF and DMARC records from guided options, use the SPF and DMARC Record Generator. To confirm DNS changes have propagated across major public resolvers, use the DNS Propagation Checker. To check a site’s SSL certificate, use the SSL Certificate Checker. For domain registration and ownership details, the WHOIS Lookup has you covered. Browse the full collection at the networking tools hub.