To check MX records for a domain, run a DNS lookup. On macOS or Linux, type dig example.com MX in a terminal. On Windows, use nslookup -type=mx example.com. Prefer a browser? Use an online MX lookup tool. Each returns the mail servers and priorities that accept mail for that domain.
What is an MX record?
An MX (Mail Exchanger) record is a DNS entry that tells sending servers which hosts accept email for a domain. Each record carries a priority number and a hostname. Lower numbers are tried first. Without at least one valid MX record, a domain cannot receive mail reliably, and messages bounce.
MX records live in the domain's DNS zone alongside A, TXT, and CNAME records. When someone sends a message to [email protected], their mail server queries DNS for the MX records of example.com, picks the lowest priority host, and opens an SMTP connection. If the lookup returns nothing, some senders fall back to the A record, but most modern setups treat a missing MX as undeliverable. Checking MX records is the fastest way to confirm a domain is wired to receive mail at all.
How to check MX records with dig
The dig command (Domain Information Groper) ships with macOS and most Linux distributions. It gives clean, scriptable output, and it is the tool most deliverability engineers reach for first. Here is the exact flow.
- Open Terminal on macOS or Linux, or any shell with dig installed.
- Type dig example.com MX and press Enter. Swap example.com for your domain.
- Read the ANSWER SECTION. Each line shows a priority and a mail host.
- Add +short to trim the noise: dig example.com MX +short returns just priorities and hostnames.
- Query a specific resolver with dig @8.8.8.8 example.com MX to rule out a stale local DNS cache.
The +short flag is handy for quick checks. Drop it when you want TTL values and the full answer section. If dig is missing on your machine, install it through bind-tools, dnsutils, or Homebrew depending on your operating system.
How to check MX records with nslookup
nslookup is the built-in option on Windows, and it also exists on macOS and Linux. Open Command Prompt or PowerShell and run nslookup -type=mx example.com. The output lists each mail exchanger with its preference value. On Windows, nslookup is the quickest path when you do not want to install anything extra.
For an interactive session, type nslookup, then set type=mx, then enter the domain. This is useful when you need to check several domains in a row. To bypass a flaky local resolver, point at a public DNS server: nslookup -type=mx example.com 1.1.1.1.
How to check MX records with an online lookup
Not everyone wants a terminal. Web-based MX lookup tools query DNS for you and render the results in a table. They are handy on a phone, on a locked-down work laptop, or when you want to share a screenshot with a teammate. Popular DNS checkers show MX priority, the resolved hostname, and sometimes the underlying IP and reverse DNS.
If your real goal is to confirm that mail will actually land, an MX lookup is only step one. A good email verifier runs the MX check for you and then goes further, opening an SMTP-level conversation to test whether the mailbox itself responds.
How do you read the MX record output?
Read MX output as pairs of numbers and hostnames. The number is the priority (also called preference): lower values are tried first, higher values act as backups. The hostname is the server that accepts mail. Multiple records mean failover. A single record is normal for many small domains.
| Field | Example value | What it means |
|---|---|---|
| Priority | 10 | Preference order. Lower is tried first. |
| Mail host | aspmx.l.google.com | The server that accepts mail for the domain. |
| TTL | 3600 | Seconds the record can be cached before a fresh lookup. |
| Multiple records | 10, 20, 30 | Backup servers for failover if the primary is down. |
Watch the trailing dot on hostnames like aspmx.l.google.com. That dot marks a fully qualified domain name and is normal in DNS output. If you see a priority but a blank or malformed host, the record is broken and mail will struggle to route.
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From MX records to real mailbox checks
An MX record confirms the domain can receive mail. It says nothing about whether [email protected] is a real, active mailbox. Catch-all domains accept everything at the SMTP layer, so a clean MX record can still hide dead addresses. This is where verification beyond DNS matters.
SMTP-level checks connect to the mail host from your MX lookup and ask whether the specific address exists. Our verification engine layers MX validation, SMTP probing, catch-all detection, and disposable-domain flags into one verdict: Deliverable, Risky, Invalid, or Unknown. Synthisia built the Free Email Verifier so teams can clean a list before a send without wiring up their own SMTP tooling.
Common MX record problems and fixes
A few MX issues surface again and again. Fixing them usually restores mail flow within one TTL window.
- No MX record: the domain cannot receive mail. Add at least one record pointing to a valid mail host.
- MX points to a CNAME: this breaks the spec. MX hosts must resolve to an A or AAAA record, not an alias.
- Wrong priority order: a backup server listed with a lower number than the primary will grab mail first. Check the numbers.
- Stale cache: after editing DNS, wait for the old TTL to expire before trusting a fresh lookup.
- Typo in the hostname: dig +short returns the exact string, so compare it character by character against your mail provider's setup.
Run one of these three checks whenever a domain looks quiet or a campaign starts bouncing. dig and nslookup take seconds, online tools need no install, and the Free Email Verifier turns a raw list into a clean, sendable one. Confirm the MX record first, then confirm the mailbox.