MX Record Checker
Check the MX records for any domain — see which mailservers receive your email and in what priority order.
About the mx record checker
MX (Mail Exchange) records tell other mail servers where to send email for your domain. They are the entry point for inbound mail — get them wrong and mail addressed to you bounces; get them subtly wrong and mail is delayed, mis-routed, or quietly black-holed.
This checker resolves the full MX record set for your domain, sorts by priority, and verifies each target hostname has an A or AAAA record so receiving servers can actually deliver to it. It also catches a handful of misconfigurations that are easy to miss: an MX target that is itself a CNAME (RFC 7505 forbids this), an MX `0` priority used as a 'no mail accepted' signal vs as a real MX, and MX records pointing to hostnames that no longer exist.
Use it when migrating providers (Google → Microsoft, or to your own infrastructure), after registering a new domain, or when inbound mail mysteriously bounces.
How it works
- Resolves MX records at the domain apex via authoritative DNS.
- Sorts results by priority (lowest = preferred).
- Resolves each MX target's A and AAAA records and reports the result.
- Detects the 'null MX' record (`. priority 0`, RFC 7505) used to signal 'this domain does not accept mail'.
- Flags MX targets that are CNAMEs (forbidden per RFC 2181) or that don't resolve at all.
Frequently asked questions
What is an MX record?
An MX (Mail Exchange) record is a DNS record listing the mail server hostnames responsible for accepting mail on behalf of a domain, along with priority numbers. Lower priority means more preferred; senders try the lowest-priority server first and fall back up the list on failure.
Should MX priority be lower or higher?
Lower numbers are preferred. An MX with priority 10 is tried before one with priority 20. Use multiple MX records with different priorities to provide failover; use multiple records at the same priority to load-balance across mail servers.
Can MX point to a CNAME?
No. RFC 2181 §10.3 states that MX records must point to canonical hostnames with A or AAAA records, not to CNAMEs. Some receivers tolerate it; many do not — pointing MX at a CNAME causes intermittent, hard-to-debug delivery failures.
What is a null MX record?
A null MX (`0 .` — priority zero, target a single dot) is the RFC 7505 standard way to declare that a domain does not accept email. Senders that respect the standard will reject mail addressed to the domain immediately rather than queuing for retries. Useful for parked domains and infrastructure-only subdomains.
How long does an MX change take to propagate?
Up to the TTL of the previous MX record set. Most providers use 1–4 hours; some use 24h or 48h. To speed up a planned migration, lower the TTL to ~300 seconds 24+ hours before the change, then change MX, then raise the TTL back. Worth doing before any provider migration.