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MX record priority explained
Reviewed by the Free Domain Mail editorial team · Updated
MX priority controls the order in which sending servers try the published mail exchangers. Lower numeric values are attempted first.
Use the provider's complete set
Equal priorities may distribute attempts; higher numbers are fallback routes only when the lower-priority target cannot accept mail.
A backup MX must still be authorized and configured to relay safely for the domain.
Test the public answer
Publish both priority and full target, then run MX Lookup from outside the DNS provider.
Do not put priority inside the hostname unless the provider's interface explicitly uses a combined value field.
Common mistakes to avoid
- Changing production DNS before recording the current values.
- Assuming a DNS record guarantees inbox placement.
- Testing before the previous TTL has expired.
Frequently asked questions
Is priority 0 always best?
It is preferred over larger values, but use the exact priorities your provider supplies.
Does MX affect outbound mail?
MX primarily directs incoming delivery; outbound authentication uses SPF, DKIM and DMARC.
Technical references
Primary specifications and provider documentation relevant to this guide: