Setting MX Records
An MX record tells the internet which mail server handles email for your domain. Without a correctly configured MX record, messages sent to your domain will bounce or disappear. Setup takes minutes if you know your mail provider's server addresses and priority values. The checker on this page validates your MX configuration and flags common errors.
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How MX Records and Priority Work
MX stands for Mail Exchange. Each MX record contains two pieces of information: a mail server hostname and a priority number. When someone sends email to your domain, the sending server looks up your MX records, sorts them by priority (lowest number first), and attempts delivery to the highest-priority server. If that server is unavailable, it tries the next one in order.
A typical setup has two MX records: a primary with priority 10 and a backup with priority 20. The numbers themselves do not matter in absolute terms — only the relative order counts. You could use 1 and 2 or 10 and 20; the effect is identical. Two records with the same priority cause sending servers to distribute mail between them roughly equally, which is how large providers handle load balancing.
MX records must point to a hostname, never directly to an IP address. This is a strict requirement defined in RFC 5321. If your mail server only has an IP address, create an A record for it first, then point the MX record at that hostname.
Common MX Mistakes That Break Email
The most frequent mistake is pointing an MX record at a CNAME. The DNS specification prohibits this, and while some resolvers tolerate it, others will fail silently, causing intermittent delivery problems that are difficult to diagnose. Always point MX records at A or AAAA records.
Another common error is leaving old MX records in place after switching email providers. If your previous provider's servers are still listed, some messages will be delivered there instead of to your new provider. After any email migration, remove all MX records belonging to the old service before adding the new ones.
Missing or incorrect SPF and DKIM records do not technically break MX delivery, but they cause receiving servers to flag your mail as suspicious. If you have set up MX records and mail is arriving but landing in spam folders, email authentication is the next step.
Changes to MX records are subject to DNS propagation. After updating, allow a few hours for global resolvers to pick up the new records before testing delivery.
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Related guides and tools
Sources
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MX record format per RFC 5321, Section 5. MX-to-CNAME prohibition per RFC 2181, Section 10.3. Priority sorting per RFC 5321, Section 5.1.
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