What does the priority number mean?

It's the MX record's preference value: lower numbers are tried first. A sending mail server attempts delivery to the lowest-priority host, and only falls back to higher-priority (larger number) hosts if that one is unreachable.

What does it mean if no MX records are found?

It usually means the domain doesn't accept email at all. Some mail servers will fall back to a domain's A record as a last resort per RFC 5321, but that's a compatibility fallback, not something to rely on for a domain that's meant to receive mail.

What is a 'null MX' record?

A record like '0 .' (priority 0, exchange a single dot) is a deliberate RFC 7505 declaration that the domain accepts no mail at all, rather than just an absence of MX records. It tells sending servers to bounce mail immediately instead of retrying, which is useful for domains that only ever send mail (or none) and want to fail fast. example.com itself publishes exactly this record.

Why do I sometimes see the same priority number on multiple records?

That's normal and means those mail servers are equally preferred; a sending server can pick between them (often at random, or round-robin) for basic load balancing across equally-ranked hosts.

MX Record Lookup - Find a Domain's Mail Servers

Overview

Introduction

Before a mail server can deliver a message to a domain, it needs to know which host actually accepts mail for it, which is exactly what an MX record answers.

This tool looks up a domain's MX records over DNS-over-HTTPS and lists them in the order a sending server would actually try them.

What Is MX Record Lookup?

An MX record lookup that queries a domain's mail exchanger records and sorts them by priority, lowest (most preferred) first.

It's part of this site's DNS & Domain Tools collection; the DNS query is a real, live request to a public resolver.

How MX Record Lookup Works

The domain is queried for its MX record type via DNS-over-HTTPS, which returns each mail server's hostname paired with a numeric priority.

Results are parsed and sorted so the most-preferred (lowest-numbered) mail server appears first, matching real delivery order.

When To Use MX Record Lookup

Use it when setting up or migrating email hosting, to confirm the MX records actually point at the provider you expect.

It's also useful for a quick sanity check when diagnosing 'mail isn't arriving' reports, to rule out a missing or misconfigured MX record.

Often used alongside DKIM Record Checker and MTA-STS Checker.

Features

Advantages

Shows records already sorted by delivery priority instead of in arbitrary DNS response order.
A single, fast lookup for confirming mail routing without a terminal or dig installed.

Limitations

Only reports what's published in DNS; it doesn't test whether the listed mail servers are actually reachable or accepting connections.
Doesn't check SPF, DKIM, or DMARC, which also affect whether mail from or to this domain is trusted.

Examples

A domain with a primary and backup mail server

Input

example.com

Output

10 → mail1.example.com
20 → mail2.example.com

mail1.example.com is tried first (priority 10); mail2.example.com is the backup (priority 20).

Best Practices & Notes

Best Practices

Verify MX records right after migrating email providers, before decommissioning the old provider's mailboxes.
Check this alongside SPF and DKIM records when setting up a new domain for outbound and inbound mail together.

Developer Notes

MX record data from DoH JSON APIs comes back as a single string like '10 mail.example.com.', so it's split on whitespace into a numeric priority and a hostname, with the trailing root dot stripped for display.

MX Record Lookup Use Cases

Confirming MX records point at the correct provider after a domain or email migration
Diagnosing inbound mail delivery failures by checking whether MX records exist at all
Auditing a newly acquired domain's existing mail configuration before making changes

Common Mistakes

Forgetting to update MX records as part of a provider migration, leaving mail routed to a decommissioned server.
Assuming a domain with no MX records can't send mail; MX only governs receiving, outbound delivery depends on the sending server's own configuration.

Tips

Check MTA-STS and DKIM for the same domain right after confirming MX, since all three are usually configured together during mail setup.

MX Record Lookup