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MX Lookup

Find the mail exchange (MX) servers for a domain or email address, with their priority values and TTLs. The lookup runs on our server.

Input TEXT
Output TEXT
Ready.

How to use the MX Lookup

  1. Enter a domain such as gmail.com or a full email address; everything before the @ is ignored.
  2. Start the lookup. Our server queries the MX records for that domain.
  3. Read each line: TTL, then the priority number and the mail server hostname.
  4. The servers are listed by priority number, lowest first, so the first line is the one senders try first.

MX lookup: find where a domain's email goes

When someone sends you an email, their server first performs an MX lookup on your domain. The MX (mail exchange) records list the servers that accept mail for the domain and a number that sets the order in which senders try them. This tool shows those records so you can confirm a new mail provider is live or diagnose bounced messages.

Priority: lower numbers win

Each MX record has a preference value, usually called priority. Sending servers try the lowest number first and move to higher numbers only if the preferred servers are unreachable. Records with the same number share the load. The numbers are relative: 10 and 20 behave exactly like 1 and 2.

Output lines are sorted by priority, lowest number first, so the line order is the order senders try the servers. A lookup for gmail.com looks like this (TTLs vary):

TYPE  TTL     VALUE
MX    515     5 gmail-smtp-in.l.google.com
MX    515     10 alt1.gmail-smtp-in.l.google.com
MX    515     20 alt2.gmail-smtp-in.l.google.com
MX    515     30 alt3.gmail-smtp-in.l.google.com
MX    515     40 alt4.gmail-smtp-in.l.google.com

Here gmail-smtp-in.l.google.com has priority 5, making it the primary server, so it is listed first.

Special cases worth knowing

  • No MX records at all. Under RFC 5321, senders then fall back to the domain's A or AAAA address. That is rarely what you want, so domains that receive mail should publish MX records explicitly.
  • Null MX. A single record with priority 0 and an empty host (written 0 . in the zone) declares that the domain accepts no email at all (RFC 7505). In the output it appears as the number 0 with no hostname.
  • MX pointing to an IP. The target must be a hostname with its own A or AAAA record. An IP address in an MX record is invalid, and the target should not be a CNAME either.

Troubleshooting checklist

  1. Confirm every MX host belongs to your current provider; leftover records from an old host can swallow mail.
  2. Resolve each target with Hostname to IP to make sure it has an address.
  3. Check the SPF record in TXT Record Lookup, since receiving servers check it against the sending host.
  4. If you just changed records, allow the old TTL to expire before judging the result.

For every record type in one place, use the full DNS lookup. On the command line, dig example.com MX +short gives the same data.

Privacy

The query runs on our server, not on your device. If you enter an email address, only the domain part is used for the lookup, and the tool does not store what you enter.

Frequently asked questions

Which MX record is used first?
The one with the lowest priority number. Senders move to higher numbers only when all servers with a lower number fail to respond.
Can I enter an email address instead of a domain?
Yes. The tool takes the part after the @ and looks up that domain, so jane@example.com checks the MX records of example.com.
What does an MX record with priority 0 and no host mean?
It is a null MX record, defined in RFC 7505. It tells senders that the domain does not accept email, so they can fail immediately instead of retrying.
Why does the lookup say no records were found?
The domain may not publish MX records, the name may be misspelled, or it may not exist. Without MX records, mail servers try the domain’s A or AAAA address instead.
How long do MX changes take to work?
Resolvers may keep the old records until the previous TTL expires, often between a few minutes and a day. Lowering the TTL before switching providers shortens that window.

Last updated October 3, 2026

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